Information Center

Glossary

abend
See abnormal end of task.
abend reason code
A 4-byte hexadecimal code that uniquely identifies a problem with DB2.
abnormal end of task (abend)
Termination of a task, job, or subsystem because of an error condition that recovery facilities cannot resolve during execution.
ACB
See application control block.
ACBGEN
See application control block generation.
access intent
Start of changeA system definition specification that indicates how a subsystem intends to use a database. During system definition, a user declares one of four levels of access intent for the subsystem. See also exclusive access, update access, read access, read-only access.End of change
access method services
Start of changeThe facility that is used to define, alter, delete, print, and reproduce VSAM key-sequenced data sets.End of change
access path
The path that is used to locate data that is specified in SQL statements. An access path can be indexed or sequential.
active IMS
  • In an RSR environment, an IMS that runs at an active site, performs production work, and is monitored by the tracking IMS. Contrast with tracking IMS.
  • In an XRF environment, an IMS that performs production work and is monitored by the alternate IMS. Contrast with alternate IMS.
  • If FDBR is used, the IMS that performs production work. The active IMS is monitored by a separate Fast Database Recovery IMS control region.
active IRLM
Start of changeThe internal resource lock manager (IRLM) that supports the active IMS in an XRF complex. See also alternate IRLM. End of change
active libraries
The libraries from which IMS draws its execution information when online change is used.
active log
The portion of the DB2 log to which log records are written as they are generated. The active log always contains the most recent log records. See also archive log.
active site
Start of changeIn a Remote Site Recovery (RSR) environment, the data-processing center that contains active IMSs.End of change
active subsystem
See active IMS.
address space
Start of changeA range of virtual storage pages that is identified by a number (ASID) and a collection of segment and page tables that map the virtual pages to real pages of the computer's memory.End of change
address space connection
The result of connecting an allied address space to DB2. See also allied address space and task control block.
address space identifier (ASID)
A unique system-assigned identifier for an address space.
ADS
See area data set.
advanced program-to-program communication (APPC)/IMS
Start of changeA part of IMS TM, using the common programming interface, which allows IMS application programs to communicate with other programs by using LU 6.2.End of change
affinity
See VGR affinity and RM affinity.
Start of changeAFTER triggerEnd of change
Start of changeA trigger that is specified to be activated after a defined trigger event (an insert, update, or delete operation on the table that is specified in a trigger definition). Contrast with BEFORE trigger and INSTEAD OF trigger.End of change
agent
In DB2, the structure that associates all processes that are involved in a DB2 unit of work. See also allied agent and system agent.
aggregate function
An operation that derives its result by using values from one or more rows. Contrast with scalar function.
AGN
See application group name.
AIB mask
Start of changeA mapping that an application program uses to interpret the application interface block (AIB).End of change
alias
Start of changeAn alternative name that can be used in SQL statements to refer to a table or view in the same or a remote DB2 subsystem. An alias can be qualified with a schema qualifier and can thereby be referenced by other users. Contrast with synonym.End of change
allied address space
Start of changeAn area of storage that is external to DB2 and that is connected to DB2. An allied address space can request DB2 services. See also address space.End of change
allied agent
An agent that represents work requests that originate in allied address spaces. See also system agent.
allied thread
A thread that originates at the local DB2 subsystem and that can access data at a remote DB2 subsystem.
allocated cursor
Start of changeA cursor that is defined for a stored procedure result set by using the SQL ALLOCATE CURSOR statement. End of change
alternate IMS
Start of changeIn an Extended Recovery Facility (XRF) environment, the IMS that monitors the active IMS and takes over production work when the active IMS fails. Contrast with active IMS.End of change
alternate IRLM
Start of changeThe internal resource lock manager (IRLM) that supports the alternate IMS in an Extended Recovery Facility (XRF) complex. See also active IRLM.End of change
alternate program communication block (alternate PCB)
Start of changeA user-defined telecommunication-program program communication block (TP PCB), defined by the user, that can be used to describe output message destinations other than the terminal that originated the input message. Where the keyword SAMETRM=YES is not implicitly or explicitly specified in a PSB, the destination of an alternate PCB can be either a logical terminal or an input transaction queue. See also modifiable alternate PCB, express alternate PCB, and alternate response PCB.End of change
alternate response PCB
Start of changeA program communication block (PCB) that defines a logical terminal and can be used instead of the I/O PCB when required to direct a response to a terminal in response mode, conversational mode, or exclusive mode.End of change
ambiguous cursor
A database cursor for which DB2 cannot determine whether it is used for update or read-only purposes.
AO
See Automated Operator.
AOI
See Automated Operator Interface.
APAR
See authorized program analysis report.
APF
See authorized program facility.
API
See application programming interface.
APPC/IMS
See advanced program-to-program communication (APPC)/IMS.
APPL
A VTAM network definition statement that is used to define DB2 to VTAM as an application program that uses SNA LU 6.2 protocols.
application
A program or set of programs that performs a task; for example, a payroll application.
application control block (ACB)
Start of changeA control block that is created from the output of DBD and PSB generation and placed in the ACB library for use during online and database batch (DBB) region type execution of IMS.End of change
application control block generation (ACBGEN)
The process by which the application control blocks are generated.
application group name (AGN)
In IMS Version 9 and earlier versions, a name that represents a defined group of IMS resources (PSBs, transaction names, and logical terminal names). Application group names are used by the Security Maintenance utility.
Start of changeapplication group name (AGN) securityEnd of change
In IMS Version 9 and earlier versions, security that is implemented by the Security Maintenance utility to limit the access to IMS resources from application programs and utilities executing in dependent regions.
application plan
The control structure that is produced during the bind process. DB2 uses the application plan to process SQL statements that it encounters during statement execution.
application process
The unit to which resources and locks are allocated. An application process involves the execution of one or more programs.
application program checkpoint
Start of changeA commit point that occurs when an application program issues a checkpoint call. IMS releases the segments that it has enqueued for the program since the last commit point; makes permanent the program's changes to the database; and, if the program processes messages, sends output messages to their destinations.End of change
application programming interface (API)
A functional interface that is supplied by the operating system or by a separately orderable licensed program that allows an application program that is written in a high-level language to use specific data or functions of the operating system or licensed program.
application program output limits
Start of changeA system definition option (SEGNO and SEGSIZE keywords) that enables users to limit the size and number of output segments that are produced by an application program. This option protects available message queue space from being depleted by a program output loop.End of change
application requester
The component on a remote system that generates DRDA requests for data on behalf of an application.
application server
The target of a request from a remote application. In the DB2 environment, the application server function is provided by the distributed data facility and is used to access DB2 data from remote applications.
APPLID name
Start of changeThe name by which VTAM identifies an IMS system for establishing sessions. The name is specified in a VTAM APPL definition statement and in the APPLID keyword of the COMM system definition macro. End of change
archive log
The portion of the DB2 log that contains log records that have been copied from the active log. See also active log.
area
Start of changeA subset of a data entry database (DEDB) that is defined as a VSAM entry-sequenced data set (ESDS). Each area in a DEDB consists of a root-addressable part, an independent-overflow part, and a sequential-dependent part. Areas contain the entire logical structure for a set of root segments and their dependent segments.End of change
area data set (ADS)
Start of changeA data set that contains a data entry database (DEDB) area. IMS can maintain up to seven copies of this data set. See also multiple area data set.End of change
area-level sharing
Start of changeSee level one data sharing.End of change
ASCII
An encoding scheme that is used to represent strings in many environments, typically on PCs and workstations. Contrast with EBCDIC and Unicode.
ASID
See address space identifier.
associated printing
Start of changeA technique for directing application program printout output to a specific printer node name. The destination print queue is specified at logon or signon time, and is created during signon of the user who created the input transaction.End of change
attachment facility
An interface between DB2 and TSO, IMS, CICS, or batch address spaces. An attachment facility allows application programs to access DB2.
attribute
A characteristic of an entity. For example, in database design, the phone number of an employee is an attribute of that employee.
attribute simulation
An MFS option that allows an application program to simulate display (video) attributes such as high intensity on printer devices.
authorization ID
Start of changeA string that can be verified for connection to DB2 and to which a set of privileges is allowed. An authorization ID can represent an individual or an organizational group.End of change
authorized program analysis report (APAR)
A report of a problem that is caused by a suspected defect in a current release of an IBM supplied program.
authorized program facility (APF)
Start of changeA facility that allows an installation to identify system or user programs that can use sensitive system functions. End of change
autologon
Start of changeThe option of IMS to automatically create a VTAM session for a non-signed-on user to whom output has been made available.End of change
Start of changeAutomated Operator (AO)End of change
An application program that can issue a subset of IMS operator commands and receive status information on the execution of the commands.
Automated Operator Interface
Start of changeAn IMS interface that allows installations to monitor and control IMS activities. The interface enables an application program, by using DL/I calls, to issue a subset of IMS operator commands and receive command responses; a user exit routine to monitor activities and take appropriate action; and operator commands, responses, and asynchronous output that is destined for the IMS master terminal to be logged to the secondary master terminal.End of change
automatic bind
Start of change(More correctly automatic rebind.) A process by which SQL statements are bound automatically (without a user issuing a BIND command) when an application process begins execution and the bound application plan or package it requires is not valid. End of change
automatic query rewrite
A process that examines an SQL statement that refers to one or more base tables or materialized query tables, and, if appropriate, rewrites the query so that it performs better.
auxiliary index
Start of changeAn index on an auxiliary table in which each index entry refers to a LOB or XML document.End of change
auxiliary table
Start of changeA table that contains columns outside the actual table in which they are defined. Auxiliary tables can contain either LOB or XML data. End of change
Start of changeavailability manager (AVM)End of change
Start of changeThe component of z/OS that performs XRF processing. Specifically, the availability manager performs I/O prevention during takeover. End of change
Start of changeAVMEnd of change
Start of changeSee availability manager.End of change
back-end system
Start of changeAn IMS in a multisystem environment that accepts transactions from the front-end system, calls application programs for transaction processing, and routes replies back to the front-end system for response to the terminal. A back-end system can also perform front-end processing. A back-end system can be another IMS that is connected by an MSC link or can be part of the same IMSplex as the front-end system. See also front-end system.End of change
backout
For DB2 The process of undoing uncommitted changes that an application process made. A backout is often performed in the event of a failure on the part of an application process, or as a result of a deadlock situation.
For IMS The process of removing all database updates that were made by an application program that terminated abnormally. See also dynamic backout.
backward log recovery
Start of changeThe final phase of restart processing during which DB2 scans the log in a backward direction to apply UNDO log records for all aborted changes.End of change
Base Primitive Environment (BPE)
Start of change A common system service base on which many other IMS components are built. BPE provides a common set of system services such as storage management, tracing, and dispatching to various components such as the IMS Common Queue Server (CQS), IMS Connect, Operations Manager (OM), Resource Manager (RM), and Structured Call Interface (SCI).End of change
base table
Start of changeA table that is created by the SQL CREATE TABLE statement and that holds persistent data. Contrast with clone table, materialized query table, result table, temporary table, and transition table.End of change
base table space
A table space that contains base tables.
basic checkpoint
A point in an application program where the work of the application is committed. Unlike with a symbolic checkpoint, you cannot restart application from a basic checkpoint.
basic edit
Start of changeAn IMS function that performs general message editing for terminal input and output messages.End of change
Start of changebasic row formatEnd of change
Start of changeA row format in which values for columns are stored in the row in the order in which the columns are defined by the CREATE TABLE statement. Contrast with reordered row format. End of change
basic sequential access method (BSAM)
An access method for storing or retrieving data blocks in a continuous sequence, using either a sequential-access or a direct-access device.
batch image copy
Start of changeA copy of a database or area that reflects the state of the data at a point when no updates were being made. The Database Image Copy utility (DFSUDMP0) creates batch image copies, which IMS utilities can use to recover from failures.End of change
batch IMS
See batch processing program.
batch message processing (BMP) program
An IMS batch processing program that has access to online databases and message queues. BMPs run online, but like programs in a batch environment, they are started with job control language (JCL). See also mixed-mode BMP.
batch-oriented BMP program
Start of changeA BMP program that has access to online databases and message queues while performing batch processing. A batch-oriented BMP does not access the IMS message queues for input or output. It can access online databases, GSAM databases, and z/OS for both input and output. See also transaction-oriented BMP.End of change
batch processing program
Start of changeAn application program that has access to databases and z/OS data management facilities but does not have access to the IMS control region or its message queues. See also batch message processing program and message processing program.End of change
Start of changeBEFORE triggerEnd of change
Start of changeA trigger that is specified to be activated before a defined trigger event (an insert, an update, or a delete operation on the table that is specified in a trigger definition). Contrast with AFTER trigger and INSTEAD OF trigger.End of change
binary large object (BLOB)
Start of changeA binary string data type that contains a sequence of bytes that can range in size from 0 bytes to 2 GB, less 1 byte. This string does not have an associated code page and character set. BLOBs can contain, for example, image, audio, or video data. In general, BLOB values are used whenever a binary string might exceed the limits of the VARBINARY type.End of change
binary string
Start of changeA sequence of bytes that is not associated with a CCSID. Binary string data type can be further classified as BINARY, VARBINARY, or BLOB.End of change
bind
Start of changeA process by which a usable control structure with SQL statements is generated; the structure is often called an access plan, an application plan, or a package. During this bind process, access paths to the data are selected, and some authorization checking is performed. See also automatic bind.End of change
bit data
Start of change
  • Data with character type CHAR or VARCHAR that is defined with the FOR BIT DATA clause. Note that using BINARY or VARBINARY rather than FOR BIT DATA is highly recommended.
  • Data with character type CHAR or VARCHAR that is defined with the FOR BIT DATA clause.
  • A form of character data. Binary data is generally more highly recommended than character-for-bit data.
End of change
BLOB
See binary large object.
block fetch
Start of changeA capability in which DB2 can retrieve, or fetch, a large set of rows together. Using block fetch can significantly reduce the number of messages that are being sent across the network. Block fetch applies only to non-rowset cursors that do not update data.End of change
Start of changeblock-level data sharingEnd of change
A method of sharing data among IMSs so that multiple application programs can access and update data concurrently between multiple IMSs.
BMP program
See batch message processing program.
bootstrap data set (BSDS)
A VSAM data set that contains name and status information for DB2 and RBA range specifications for all active and archive log data sets. The BSDS also contains passwords for the DB2 directory and catalog, and lists of conditional restart and checkpoint records.
BPE
See Base Primitive Environment.
BSAM
See basic sequential access method.
BSDS
See bootstrap data set.
buffer handler
Start of changeAn internal component of IMS that manages buffers. The buffer handler maintains pools of buffers. When a buffer is needed, the buffer handler selects the buffer at the bottom of the use chain.End of change
buffer invalidation
Start of changeTo prevent application programs from using invalid data in a sysplex data-sharing environment, IMS marks all copies of data in IMS buffers as invalid after a sharing IMS updates that data.End of change
buffer lookaside
For shared VSO DEDB areas, an option that tells IMS to check the private buffer pools for requested data before retrieving data from the coupling facility.
buffer pool
Start of changeFor DB2 An area of memory into which data pages are read, modified, and held during processing. End of change
For IMS A set of buffers that contains buffers of the same length.
built-in data type
Start of changeA data type that IBM supplies. Among the built-in data types for DB2 for z/OS are string, numeric, XML, ROWID, and datetime. Contrast with distinct type.End of change
built-in function
Start of changeA function that is generated by DB2 and that is in the SYSIBM schema. Contrast with user-defined function. See also function, cast function, external function, sourced function, and SQL function.End of change
business dimension
A category of data, such as products or time periods, that an organization might want to analyze.
CA
See change accumulation.
cache structure
For DB2 A coupling facility structure that stores data that can be available to all members of a Sysplex. A DB2 data sharing group uses cache structures as group buffer pools.
Start of changeFor IMS One of the separate sections of the coupling facility storage. The coupling facility storage is divided, under installation control, into distinct sections called structures. End of change
CAF
See call attachment facility.
callable services
Start of changeServices that are provided by IMS for use by IMS exit routines. These services provide clearly defined interfaces that allow exit routines to request various functions, such as acquiring storage or finding an IMS control block.End of change
call attachment facility (CAF)
Start of changeA DB2 attachment facility for application programs that run in TSO or z/OS batch. The CAF is an alternative to the DSN command processor and provides greater control over the execution environment. Contrast with Recoverable Resource Manager Services attachment facility.End of change
call-level interface (CLI)
A callable application programming interface (API) for database access, which is an alternative to using embedded SQL.
cascade delete
A process by which DB2 enforces referential constraints by deleting all descendent rows of a deleted parent row.
CASE expression
An expression that is selected based on the evaluation of one or more conditions.
cast function
A function that is used to convert instances of a (source) data type into instances of a different (target) data type.
castout
The DB2 process of writing changed pages from a group buffer pool to disk.
castout owner
The DB2 member that is responsible for casting out a particular page set or partition.
catalog
In DB2, a collection of tables that contains descriptions of objects such as tables, views, and indexes.
catalog table
Any table in the DB2 catalog.
catch-up processing
Start of changeIn an RSR environment, the process by which tracked log data is used to make all recoverable resources (for example, shadow databases) current with those resources on the active IMS.End of change
CCB
See conversation control block.
CCSID
See coded character set identifier.
CCTL
See coordinator controller.
CDB
See communications database.
CDRA
See Character Data Representation Architecture.
CEC
See central processor complex.
central electronic complex (CEC)
See central processor complex.
central processor complex (CPC)
A physical collection of hardware that consists of main storage, one or more central processors, timers, and channels.
central processor (CP)
The part of the computer that contains the sequencing and processing facilities for instruction execution, initial program load, and other machine operations.
CF
See coupling facility.
CFRM
See coupling facility resource management.
CFRM policy
The allocation rules for a coupling facility structure that are declared by a z/OS administrator.
change accumulation (CA)
Start of changeThe process of creating a compacted version of one or more IMS log data sets by eliminating records not related to recovery, and by merging multiple changes to a single segment into a single change.End of change
character conversion
The process of changing characters from one encoding scheme to another.
Character Data Representation Architecture (CDRA)
An architecture that is used to achieve consistent representation, processing, and interchange of string data.
character large object (CLOB)
Start of changeA character string data type that contains a sequence of bytes that represent characters (single-byte, multibyte, or both) that can range in size from 0 bytes to 2 GB, less 1 byte. In general, CLOB values are used whenever a character string might exceed the limits of the VARCHAR type.End of change
character set
A defined set of characters.
character string
Start of changeA sequence of bytes that represent bit data, single-byte characters, or a mixture of single-byte and multibyte characters. Character data can be further classified as CHARACTER, VARCHAR, or CLOB.End of change
check constraint
A user-defined constraint that specifies the values that specific columns of a base table can contain.
check integrity
The condition that exists when each row in a table conforms to the check constraints that are defined on that table.
check pending
A state of a table space or partition that prevents its use by some utilities and by some SQL statements because of rows that violate referential constraints, check constraints, or both.
checkpoint
Start of changeA point at which DB2 records status information on the DB2 log; the recovery process uses this information if DB2 abnormally terminates.End of change
checkpoint data set
A local data set that contains Common Queue Server (CQS) system checkpoint information about a group of shared queues.
child lock
For explicit hierarchical locking, a lock that is held on either a table, page, row, or a large object (LOB). Each child lock has a parent lock. See also parent lock.
child segment
In a database, any segment that is dependent on another segment above it (its parent) in the hierarchy.
CI
See control interval.
CIC
See Concurrent Image Copy.
CICS
Start of changeRepresents (in this information): CICS Transaction Server for z/OS: Customer Information Control System Transaction Server for z/OS.End of change
CICS attachment facility
Start of changeA facility that provides a multithread connection to DB2 to allow applications that run in the CICS environment to execute DB2 statements.End of change
CID
Start of changeThe VTAM/NCP communication ID. This value is given to IMS and is used by VTAM and IMS to identify a session between IMS and a VTAM logical unit.End of change
claim
A notification to DB2 that an object is being accessed. Claims prevent drains from occurring until the claim is released, which usually occurs at a commit point. Contrast with drain.
claim class
A specific type of object access that can be one of the following isolation levels:
  • Cursor stability (CS)
  • Repeatable read (RR)
  • Write
class
Start of changeAn attribute that is related to a transaction code and a message region that is used to determine scheduling. See also message class and region class.End of change
classic command
A supported non-IMSplex command. A classic command generally requires a leading slash, for example, /DBRECOVERY.
class of service
A VTAM term for a list of routes through a network, arranged in an order of preference for their use.
class-3 terminal
Start of changeA terminal that communicates with XRF IMS but whose sessions are not automatically reestablished at takeover. End of change
class-1 terminal
Start of changeA terminal for which the alternate IMS pre-opens backup sessions for the primary sessions that the active IMS opens; VTAM/NCP switches sessions from primary to backup at takeover.End of change
class-2 terminal
Start of changeA terminal for which IMS in the alternate reestablishes service at takeover.End of change
clause
In SQL, a distinct part of a statement, such as a SELECT clause or a WHERE clause.
CLB
See Communication Line Block.
CLI
See call-level interface.
client
See requester.
CLOB
See character large object.
cloned IMSplex
A group of IMSs in a sysplex that share databases, queues, or both, and have identical resource definitions.
Start of changeclone objectEnd of change
Start of changeAn object that is associated with a clone table, including the clone table itself and check constraints, indexes, and BEFORE triggers on the clone table. End of change
Start of changeclone tableEnd of change
Start of changeA table that is structurally identical to a base table. The base and clone table each have separate underlying VSAM data sets, which are identified by their data set instance numbers. Contrast with base table.End of change
closed application
An application that requires exclusive use of certain statements on certain DB2 objects, so that the objects are managed solely through the external interface of that application.
clustering index
Start of changeAn index that determines how rows are physically ordered (clustered) in a table space. If a clustering index on a partitioned table is not a partitioning index, the rows are ordered in cluster sequence within each data partition instead of spanning partitions. End of change
CM
Start of changeSee compatibility mode.End of change
CM*
Start of changeSee compatibility mode*.End of change
C++ member
A data object or function in a structure, union, or class.
C++ member function
An operator or function that is declared as a member of a class. A member function has access to the private and protected data members and to the member functions of objects in its class. Member functions are also called methods.
CNT
See Communication Name Table.
C++ object
A region of storage. An object is created when a variable is defined or a new function is invoked.
An instance of a class.
coded character set
A set of unambiguous rules that establish a character set and the one-to-one relationships between the characters of the set and their coded representations.
coded character set identifier (CCSID)
A 16-bit number that uniquely identifies a coded representation of graphic characters. It designates an encoding scheme identifier and one or more pairs that consist of a character set identifier and an associated code page identifier.
code page
A set of assignments of characters to code points. Within a code page, each code point has only one specific meaning. In EBCDIC, for example, the character A is assigned code point X'C1', and character B is assigned code point X'C2'.
code point
In CDRA, a unique bit pattern that represents a character in a code page.
code unit
Start of changeThe fundamental binary width in a computer architecture that is used for representing character data, such as 7 bits, 8 bits, 16 bits, or 32 bits. Depending on the character encoding form that is used, each code point in a coded character set can be represented by one or more code units. End of change
coexistence
During migration, the period of time in which two releases exist in the same data sharing group.
cold queue
A CQS private queue type that contains indoubt data objects for a client that cold started or a CQS that cold started.
cold start
For DB2 A process by which DB2 restarts without processing any log records. Contrast with warm start.
Start of changeFor IMS The process of starting IMS when it is initialized for the first time or when an error condition prevents a warm start or an emergency restart. See also emergency restart and normal restart.End of change
collection
A group of packages that have the same qualifier.
column
The vertical component of a table. A column has a name and a particular data type (for example, character, decimal, or integer).
column function
See aggregate function.
"come from" checking
An LU 6.2 security option that defines a list of authorization IDs that are allowed to connect to DB2 from a partner LU.
command
A DB2 operator command or a DSN subcommand. A command is distinct from an SQL statement.
Command Center
Start of changeA component of the Control Center for IMS that is used to issue IMSplex commands from both a workstation or multiple IMS systems.End of change
command code
The portion of the segment search argument (SSA) that enables an application program to access a database segment based on some variation in either the call function, the segment qualification, or the setting of parentage.
command master
Start of changeIn an IMSplex, the IMS that an OM designates to process a command when a command is issued through the OM API. Commands are routed to all IMS systems that are registered for the command and, if the command requires only one IMS to process it, the command master processes the command.End of change
command prefix
Start of changeA 1- to 8-character command identifier. The command prefix distinguishes the command as belonging to an application or subsystem rather than to z/OS.End of change
Start of changecommand processing clientEnd of change
An entity that can process commands or do other work as directed by an OM. In an IMSplex, an IMS control region is a command processing client.
command recognition character (CRC)
A character that permits a z/OS console operator or an IMS subsystem user to route DB2 commands to specific DB2 subsystems.
command scope
The scope of command operation in a data sharing group.
Start of changecommand significant statusEnd of change
The command status that is associated with a resource. For example, the status of STOP, TRACE, and MFSTEST commands. If a resource structure is defined, the recovery of command significant status is always maintained globally by the RM in the resource structure. See also end-user significant status.
commit
For DB2 The operation that ends a unit of work by releasing locks so that the database changes that are made by that unit of work can be perceived by other processes. Contrast with rollback.
For IMS To make changes permanent for a resource in order to establish a new consistent state.
commit point
For DB2 A point in time when data is considered consistent.
Start of changeFor IMS The point at which an application program commits that a section of work is done and that the data it has modified or created is consistent and complete. The application program's output, which has been held until that time, is sent to its destinations, its input is removed from the message queues, and its database updates are confirmed and made available to other applications. A commit point occurs when a program terminates normally or when it issues a checkpoint call or command. If a program processes messages, a commit point might also occur when it retrieves a new message.End of change
commit processing
The processing that IMS performs at a commit point.
Common Queue Server (CQS)
Start of changeThe address space that manages the shared queues (data objects that are stored in a coupling facility list structure) for its clients (IMS).End of change
common service area (CSA)
Start of changeIn z/OS, a part of the common area that contains data areas that are addressable by all address spaces. Most DB2 use is in the extended CSA, which is above the 16-MB line. End of change
Common Service Layer (CSL)
Start of changeA collection of IMS manager address spaces that provide the infrastructure that is needed for systems management tasks. The CSL address spaces include RM, OM, and SCI. The CSL is built on the Base Primitive Environment (BPE) layer.End of change
Start of changeCommon Service Layer (CSL) clientEnd of change
A z/OS address space that uses the services that are provided by the Common Service Layer (CSL). The IMS control region is an example of a CSL client.
Communication Line Block (CLB)
Start of change An IMS control block that represents a VTAM node or a BTAM line. Each VTAM node or BTAM line has a single CLB. For VTAM, the block is one of several blocks that are part of the VTCB control block. The CLB represents the TM task in the IMS system for the node or line, and also contains many other fields that pertain to the node or line.End of change
Communication Name Table (CNT)
An IMS control block that represents a logical terminal.
communications database (CDB)
A set of tables in the DB2 catalog that are used to establish conversations with remote database management systems.
comparison operator
A token (such as =, >, or <) that is used to specify a relationship between two values.
Start of changecompatibility mode* (CM*)End of change
Start of changeA stage of the version-to-version migration process that applies to a DB2 subsystem or data sharing group that was in enabling-new-function mode (ENFM), enabling-new-function mode* (ENFM*), or new-function mode (NFM) at one time. Fallback to a prior version is not supported. When in compatibility mode*, a DB2 data sharing group cannot coexist with members that are still at the prior version level. Contrast with compatibility mode, enabling-new-function mode, enabling-new-function mode*, and new-function mode. End of change
Start of changecompatibility mode (CM)End of change
Start of changeThe first stage of the version-to-version migration process. In a DB2 data sharing group, members in compatibility mode can coexist with members that are still at the prior version level. Fallback to the prior version is also supported. When in compatibility mode, the DB2 subsystem cannot use any new functions of the new version. Contrast with compatibility mode*, enabling-new-function mode, enabling-new-function mode*, and new-function mode. End of change
composite key
Start of changeAn ordered set of key columns or expressions of the same table. End of change
compression dictionary
The dictionary that controls the process of compression and decompression. This dictionary is created from the data in the table space or table space partition.
concatenated key
Start of changeThe key that is constructed to access a particular segment. A concatenated key consists of the key fields, including that of the root segment and successive children, down to the accessed segment.End of change
concurrency
The shared use of resources by more than one application process at the same time.
Start of changeconcurrent image copy (CIC)End of change
Start of changeA batch utility program that enables you to make a copy of OSAM data sets and VSAM entry-sequenced DBDSs, whether or not IMS is running and the database is online.End of change
conditional restart
A DB2 restart that is directed by a user-defined conditional restart control record (CRCR).
connection
In SNA, the existence of a communication path between two partner LUs that allows information to be exchanged (for example, two DB2 subsystems that are connected and communicating by way of a conversation).
connection context
In SQLJ, a Java object that represents a connection to a data source.
connection declaration clause
In SQLJ, a statement that declares a connection to a data source.
connection handle
The data object containing information that is associated with a connection that DB2 ODBC manages. This includes general status information, transaction status, and diagnostic information.
connection ID
An identifier that is supplied by the attachment facility and that is associated with a specific address space connection.
consistency token
A timestamp that is used to generate the version identifier for an application. See also version.
constant
A language element that specifies an unchanging value. Constants are classified as string constants or numeric constants. Contrast with variable.
constraint
A rule that limits the values that can be inserted, deleted, or updated in a table. See referential constraint, check constraint, and unique constraint.
context
Start of changeAn application's logical connection to the data source and associated DB2 ODBC connection information that allows the application to direct its operations to a data source. A DB2 ODBC context represents a DB2 thread. End of change
contracting conversion
Start of changeA process that occurs when the length of a converted string is smaller than that of the source string. For example, this process occurs when an EBCDIC mixed-data string that contains DBCS characters is converted to ASCII mixed data; the converted string is shorter because the shift codes are removed.End of change
Start of changeControl Center for IMSEnd of change
Start of changeA single point of control with a graphical interface that simplifies system management tasks in an IMSplex environment. Administrators can work with a consolidated system view and manage all their IMS systems from a single workstation.End of change
control interval (CI)
For DB2
  • A unit of information that VSAM transfers between virtual and auxiliary storage.
  • In a key-sequenced data set or file, the set of records that an entry in the sequence-set index record points to.
Start of changeFor IMS A fixed-length area of direct access storage in which VSAM stores records and creates distributed free space. Also, in a key-sequenced data set or file, the set of records that are pointed to by an entry in the sequence-set index record. The control interval is the unit of information that VSAM transmits to or from direct access storage. A control interval always comprises an integral number of physical records.End of change
control interval update sequence number (CUSN)
Start of changeAn indicator that is used in a data-sharing environment to determine which sharing partner last read a CI. IMS compares the value of the CUSN for each CI to determine whether a CI should be updated during area restart or recovery. End of change
control region
The z/OS main storage region that contains the IMS control program.
conversation
For DB2 Communication, which is based on LU 6.2 or Advanced Program-to-Program Communication (APPC), between an application and a remote transaction program over an SNA logical unit-to-logical unit (LU-LU) session that allows communication while processing a transaction.
Start of changeFor IMS A dialog between a terminal and a message processing program using IMS conversational processing facilities. Also, a dialog between an LU 6.2 program and an IMS application program. A conversation between a terminal and a message processing program is significant status that is kept in the RM, if the RM is used. Status for a held conversation is not kept in the RM. The IMS conversation is represented by a CCB. See also conversational processing.End of change
conversational processing
Start of changeAn optional facility that allows an application program to accumulate information acquired through multiple interchanges with a terminal, even though the program terminates between interchanges. Conversation information for the active and held conversations is significant status that can optionally be kept in the RM if a status recovery mode of GLOBAL is selected.End of change
conversation control block (CCB)
An IMS control block that represents a conversation between a terminal and an application program.
coordinated online change
See global online change.
coordinator
The system component that coordinates the commit or rollback of a unit of work that includes work that is done on one or more other systems.
coordinator controller (CCTL)
Start of changeA z/OS subsystem that consists of the database resource adapter (DRA) and a transaction management subsystem, such as CICS. A CCTL provides communications and transaction management services for a DBCTL environment, which has no transaction management facilities of its own.End of change
coprocessor
Start of changeSee SQL statement coprocessor.End of change
copy pool
Start of changeA collection of names of storage groups that are processed collectively for fast replication operations. End of change
copy target
A named set of SMS storage groups that are to be used as containers for copy pool volume copies. A copy target is an SMS construct that lets you define which storage groups are to be used as containers for volumes that are copied by using FlashCopy functions.
copy version
A point-in-time FlashCopy copy that is managed by HSM. Each copy pool has a version parameter that specifies the number of copy versions to be maintained on disk.
correlated columns
A relationship between the value of one column and the value of another column.
correlated subquery
A subquery (part of a WHERE or HAVING clause) that is applied to a row or group of rows of a table or view that is named in an outer subselect statement.
correlation ID
An identifier that is associated with a specific thread. In TSO, it is either an authorization ID or the job name.
correlation name
Start of changeAn identifier that is specified and used within a single SQL statement as the exposed name for objects such as a table, view, table function reference, nested table expression, or result of a data change statement. Correlation names are useful in an SQL statement to allow two distinct references to the same base table and to allow an alternative name to be used to represent an object. End of change
cost category
A category into which DB2 places cost estimates for SQL statements at the time the statement is bound. The cost category is externalized in the COST_CATEGORY column of the DSN_STATEMNT_TABLE when a statement is explained.
coupling facility
Start of changeFor DB2 A special PR/SM logical partition (LPAR) that runs the coupling facility control program and provides high-speed caching, list processing, and locking functions in a Parallel Sysplex. End of change
For IMS A special logical partition that provides high-speed caching, list processing, and locking functions in a sysplex. IMS saves global information in the coupling facility, so all the IMSs in the IMSplex have access to the global information.
coupling facility resource management (CFRM)
A component of z/OS that provides the services to manage coupling facility resources in a Parallel Sysplex. This management includes the enforcement of CFRM policies to ensure that the coupling facility and structure requirements are satisfied.
covered database
A database or area in an RSR environment that is tracked by a tracking IMS. Recovery information is not maintained by the tracking IMS for databases or areas that are not covered.
CP
See central processor.
CPC
See central processor complex.
CPI Communications driven application program
An application program that uses CPI Communications calls to receive an incoming message and to send a reply.
CQS
See Common Queue Server.
CQS restart
Start of changeThe process by which CQS starts: either a cold start or a warm start. During a CQS warm start, the CQS environment is restored to its state when CQS terminated. During a CQS cold start, the CQS environment is not restored to its previous state; it is reinitialized.End of change
CRC
See command recognition character.
created temporary table
A persistent table that holds temporary data and is defined with the SQL statement CREATE GLOBAL TEMPORARY TABLE. Information about created temporary tables is stored in the DB2 catalog and can be shared across application processes. Contrast with declared temporary table. See also temporary table.
cross-system coupling facility (XCF)
A component of z/OS that provides functions to support cooperation between authorized programs that run within a Sysplex.
cross-system extended services (XES)
A set of z/OS services that allow multiple instances of an application or subsystem, running on different systems in a Sysplex environment, to implement high-performance, high-availability data sharing by using a coupling facility.
CS
See cursor stability.
CSA
See common service area.
CSL
See Common Service Layer.
CSL component
An IMSplex member type that is part of the CSL: OM, RM, or SCI.
CT
See cursor table.
current data
Data within a host structure that is current with (identical to) the data within the base table.
current position
Start of changeIn an IMS database, the place immediately preceding the segment occurrence that IMS retrieves if you immediately issue an unqualified retrieval call.End of change
current status rebuild
The second phase of restart processing during which the status of the subsystem is reconstructed from information on the log.
cursor
Start of changeFor DB2 A control structure that an application program uses to point to a single row or multiple rows within some ordered set of rows of a result table. A cursor can be used to retrieve, update, or delete rows from a result table.End of change
For IMS During a HALDB online reorganization, a marker in a database partition that separates the copied database records from the records that have not been copied. The cursor indicates the progress of the reorganization through the HALDB partition.
cursor-active status
Start of changeFor HALDB online reorganization, the status in the RECON data set that tells DBRC that an online reorganization has started.End of change
cursor sensitivity
The degree to which database updates are visible to the subsequent FETCH statements in a cursor.
cursor stability (CS)
The isolation level that provides maximum concurrency without the ability to read uncommitted data. With cursor stability, a unit of work holds locks only on its uncommitted changes and on the current row of each of its cursors. See also read stability, repeatable read, and uncommitted read.
cursor table (CT)
Start of changeThe internal representation of a cursor. End of change
CUSN
Start of changeSee control interval update sequence number. End of change
cycle
Start of changeA set of tables that can be ordered so that each table is a descendent of the one before it, and the first table is a descendent of the last table. A self-referencing table is a cycle with a single member. See also referential cycle.End of change
database
For DB2 A collection of tables, or a collection of table spaces and index spaces.
Start of changeFor IMS A collection of data that is arranged in a hierarchical (tree) structure. At each level of the hierarchy, data is related to, and dependent on, data at the higher level of the hierarchy. Data is stored within the database only once and is available to any user who is authorized to use it. Users do not need to have personal copies of the data.End of change
database access thread (DBAT)
Start of changeA thread that accesses data at the local subsystem on behalf of a remote subsystem. End of change
database administrator (DBA)
An individual who is responsible for designing, developing, operating, safeguarding, maintaining, and using a database.
database alias
The name of the target server if it is different from the location name. The database alias is used to provide the name of the database server as it is known to the network.
Database Control (DBCTL)
Start of changeAn environment that allows full-function databases and DEDBs to be accessed from one or more transaction management subsystems.End of change
Start of changeDatabase Control (DBCTL) environmentEnd of change
Start of changeThe IMS DB/DC environment without the message handling and queue management capabilities.End of change
database data set (DBDS)
Start of changeA data set that contains some or all of the database records that are stored in a full-function database. Other types of data sets that are used in IMS databases include Fast Path area data sets, HALDB indirect list data sets, and HALDB primary index data sets.End of change
database description (DBD)
The collection of macro parameter statements that define the characteristics of a database, such as the database's organization and access method, the segments and fields in a database record, and the relationship between types of segments.
database description generation (DBDGEN)
The process by which a DBD is created.
database descriptor (DBD)
An internal representation of a DB2 database definition, which reflects the data definition that is in the DB2 catalog. The objects that are defined in a database descriptor are table spaces, tables, indexes, index spaces, relationships, check constraints, and triggers. A DBD also contains information about accessing tables in the database.
database exception status
In a data sharing environment, an indication that something is wrong with a database.
database identifier (DBID)
An internal identifier of the database.
database integrity
Start of changeThe protection of data items in a database while they are available to any application program. This protection includes the isolation of effects of concurrent updates to a database by two or more application programs.End of change
Start of changedatabase-level data sharingEnd of change
A kind of data sharing that enables application programs in one IMS to read data while another program in another IMS reads from the same database or updates it.
Start of changedatabase-level trackingEnd of change
In an RSR environment, a tracking subsystem that tracks the active subsystem's databases or areas. See also recovery-level tracking.
database management system (DBMS)
A software system that controls the creation, organization, and modification of a database and the access to the data that is stored within it.
database position
A program's place in the database after a DL/I call. IMS keeps track of the program's position in the database in order to process DL/I calls.
database program communication block (DB PCB)
Start of changeThe PCB that describes an application program's interface to a database. One DB PCB is required for each database view that is used by the application program. End of change
database record
Start of changeIn a database, a collection of segments that contains one occurrence of the root segment type and all of its dependents arranged in a hierarchic sequence. A database record can be a physical database record or a logical database record. See also physical database record and logical database record.End of change
database recovery
Start of changeThe process of restoring a physically or logically damaged DBDS by merging an image copy and logs or change accumulation data sets.End of change
Database Recovery Control (DBRC)
Start of changeA feature of the IMS Database Manager that facilitates easier recovery of IMS databases. DBRC maintains information that is required for database recoveries, generates recovery control statements, verifies recovery input, maintains a separate change log for database data sets, and supports sharing of IMS databases and areas by multiple IMS subsystems.End of change
database reorganization
The process of unloading and reloading a database to optimize physical segment adjacency or to modify the DBD.
database request module (DBRM)
A data set member that is created by the DB2 precompiler and that contains information about SQL statements. DBRMs are used in the bind process.
database resource adapter (DRA)
Start of changeAn interface to IMS DB full-function databases and DEDBs. The DRA can be used by a coordinator controller (CCTL) or by a z/OS application program that uses the ODBA interface. End of change
database segment
The unit of access; the smallest amount of data that can be transferred by one IMS operation.
database server
The target of a request from a local application or a remote intermediate database server.
data communication program communication block (DC PCB)
Start of changeObsolete term. See telecommunication program PCB.End of change
Data Communications Control (DCCTL)
A subsystem that allows IMS TM to act as a stand-alone, full-function transaction manager that can connect to DB2 or other external subsystems.
data currency
The state in which the data that is retrieved into a host variable in a program is a copy of the data in the base table.
data dictionary
A repository of information about an organization's application programs, databases, logical data models, users, and authorizations.
data element
A unit of storage in a coupling facility list structure that makes up a data entry.
data entry
Start of changePart of a coupling facility list structure list entry that is used to hold user-specified data.End of change
data entry database (DEDB)
Start of changeA direct-access database that consists of one or more areas, with each area containing both root segments and dependent segments. DEDBs use a data structure that allows them to be used for both hierarchic processing and journaling. The database is accessed by using the VSAM Media Manager. End of change
data independence
The concept of separating the definitions of logical and physical data such that application programs do not depend on where or how physical units of data are stored; the reduction of application program modification in data storage structure and access strategy.
Data Language/I (DL/I)
Start of changeThe IMS data manipulation language, which is a common high-level interface between a user application and IMS. DL/I calls are invoked from application programs that are written in languages such as Java, PL/I, COBOL, VS Pascal, C, and Ada. DL/I can also be invoked from assembler language application programs by subroutine calls. IMS lets the user define data structures, relate structures to the application, load structures, and reorganize structures.End of change
data management block (DMB)
Start of changeAn IMS control block in main storage that describes and controls a physical database. A DMB is constructed from information that is obtained from the ACB library or the DBD library.End of change
data object
Start of changeA piece of client data that is placed on the coupling facility by CQS as a result of a CQSPUT request or a CQSUPD request. From an IMS shared queues point of view, a data object contains one part or all of an IMS message or an entire EMH message. From an IMS Resource Manager point of view, a data object contains information about an IMS resource such as a transaction or a user.End of change
data partition
A VSAM data set that is contained within a partitioned table space.
data-partitioned secondary index (DPSI)
A secondary index that is partitioned according to the underlying data. Contrast with nonpartitioned secondary index.
data set group
Start of changeAn operating system data set that contains a subset of a database with one or more unique segment types. A database always consists of at least one data set group. See also primary data set group and secondary data set group.End of change
Start of changedata set instance numberEnd of change
Start of changeA number that indicates the data set that contains the data for an object.End of change
Start of changedata set sequence number (DSSN)End of change
A number, maintained by DBRC in the RECON data set, that counts when an application opens a database for update.
data sharing
For DB2 A function of DB2 for z/OS that enables applications on different DB2 subsystems to read from and write to the same data concurrently.
Start of changeFor IMS The concurrent access of databases by two or more IMSs. The IMSs can be in one operating system image or in separate operating system images. The IMSs can share data at two levels: the database level and the block level. See block-level sharing and database-level sharing.End of change
Start of changedata-sharing groupEnd of change
For DB2 A collection of one or more DB2 subsystems that directly access and change the same data while maintaining data integrity.
Start of changeFor IMS The components that are involved in sysplex data sharing. Among the components are the sharing IMSs, the IRLMs they use, the lock, OSAM, and VSAM structures in the coupling facility, and a single set of DBRC RECON data sets.End of change
data sharing member
A DB2 subsystem that is assigned by XCF services to a data sharing group.
data source
A local or remote relational or non-relational data manager that is capable of supporting data access via an ODBC driver that supports the ODBC APIs. In the case of DB2 for z/OS, the data sources are always relational database managers.
data transparency
Start of changeAn attribute of an input message that causes ISC edit to route the message to its destination without examination or modification.End of change
data type
Start of changeAn attribute of columns, constants, variables, parameters, special registers, and the results of functions and expressions. End of change
data warehouse
A system that provides critical business information to an organization. The data warehouse system cleanses the data for accuracy and currency, and then presents the data to decision makers so that they can interpret and use it effectively and efficiently.
DBA
See database administrator.
DBAT
Start of changeSee database access thread. End of change
DBB (Database Management Batch)
Start of changeOne of two batch regions (the other being a DL/I batch region). DBB is an execution parameter. DBB batch jobs contain JCL DD statements for the ACB library.End of change
DB2 catalog
A collection of tables that are maintained by DB2 and contain descriptions of DB2 objects, such as tables, views, and indexes.
DBCLOB
See double-byte character large object.
DB2 command
An instruction to the DB2 subsystem that a user enters to start or stop DB2, to display information on current users, to start or stop databases, to display information on the status of databases, and so on.
DBCS
See double-byte character set.
DBCS/EBCDIC mixed field
Start of changeA field that contains both DBCS and EBCDIC data. The DBCS portions should always be enclosed with SO/SI control characters in both inbound and outbound data. In the case of inbound data, the control characters are automatically created by the terminal. End of change
DBCTL
See Database Control.
DBD
See database descriptor.
DB (database) monitor
See IMS Monitor.
DB/DC
Start of changeDatabase/data communication.End of change
DBDGEN
See database description generation.
DBDS
See database data set.
DB2I
See DB2 Interactive.
DBID
See database identifier.
DB2 Interactive (DB2I)
An interactive service within DB2 that facilitates the execution of SQL statements, DB2 (operator) commands, and programmer commands, and the invocation of utilities.
DBMS
See database management system.
DB PCB
See database program communication block.
DBRC
See Database Recovery Control.
DBRC API
An assembler macro interface to DBRC that user-written application programs use to obtain services from DBRC.
Start of changeDBRC groupEnd of change
Start of changeIn IMS Version 10, one or more DBRC instances that share a single RECON data set in an IMSplex environment. Each DBRC group has a group identifier (GROUP ID), which is unique for that group. DBRC groups are used by DBRC, whether or not parallel RECON access is enabled.End of change
Start of changeDBRC requestEnd of change
Start of changeAn action (command process, query, and update) that is asked of DBRC by IMS, DBRC application programs, and jobs.End of change
DBRM
See database request module.
DB2 thread
Start of changeThe database manager structure that describes an application's connection, traces its progress, processes resource functions, and delimits its accessibility to the database manager resources and services. Most DB2 for z/OS functions execute under a thread structure.End of change
DCCTL
See Data Communications Control.
DCLGEN
See declarations generator.
Start of changeDC PCBEnd of change
Start of changeObsolete term. See telecommunication program PCB.End of change
Start of changeDCTEnd of change
Start of changeSee device characteristics table.End of change
DDF
See distributed data facility.
deadlock
Unresolvable contention for the use of a resource, such as a table or an index.
declarations generator (DCLGEN)
A subcomponent of DB2 that generates SQL table declarations and COBOL, C, or PL/I data structure declarations that conform to the table. The declarations are generated from DB2 system catalog information.
declared temporary table
A non-persistent table that holds temporary data and is defined with the SQL statement DECLARE GLOBAL TEMPORARY TABLE. Information about declared temporary tables is not stored in the DB2 catalog and can be used only by the application process that issued the DECLARE statement. Contrast with created temporary table. See also temporary table.
DEDB
See data entry database.
default literal
In MFS, a literal field that MFS inserts into an input message when no data for the field is received from the terminal. See also explicit literal and system literal.
default system control area (DSCA)
Start of changeIn MFS, part of the device output format (DOF) that causes specific terminal functions to be performed if the destination terminal has the required features. See also system control area.End of change
default terminal security
The basic system security that prohibits the entry of certain commands from any terminal other than the master terminal.
default value
Start of changeA predetermined value, attribute, or option that is assumed when no other value is specified. A default value can be defined for column data in DB2 tables by specifying the DEFAULT keyword in an SQL statement that changes data (such as INSERT, UPDATE, and MERGE).End of change
deferred embedded SQL
SQL statements that are neither fully static nor fully dynamic. These statements are embedded within an application and are prepared during the execution of the application.
deferred update
A Fast Path capability that keeps updates to databases in main storage buffers until a synchronization point is reached. Synchronization point processing schedules the VSAM writes and response messages to terminals after physically logging the changed data.
deferred write
The process of asynchronously writing changed data pages to disk.
degree of parallelism
The number of concurrently executed operations that are initiated to process a query.
delete hole
The location on which a cursor is positioned when a row in a result table is refetched and the row no longer exists on the base table. See also update hole.
delete rule
The rule that tells DB2 what to do to a dependent row when a parent row is deleted. Delete rules include CASCADE, RESTRICT, SET NULL, or NO ACTION.
delete trigger
Start of changeA trigger that is defined with the triggering delete SQL operation.End of change
delimited identifier
Start of changeA sequence of characters that are enclosed within escape characters.End of change
delimiter token
A string constant, a delimited identifier, an operator symbol, or any of the special characters that are shown in DB2 syntax diagrams.
denormalization
The intentional duplication of columns in multiple tables to increase data redundancy. Denormalization is sometimes necessary to minimize performance problems. Contrast with normalization.
dependent
An object (row, table, or table space) that has at least one parent. The object is also said to be a dependent (row, table, or table space) of its parent. See also parent row, parent table, and parent table space.
dependent region
An address space, managed by the IMS control region, where IMS application programs run. Dependent region types are MPP, BMP, IFP, JMP, and JBP.
dependent row
A row that contains a foreign key that matches the value of a primary key in the parent row.
dependent segment
Start of changeIn a database, a segment that relies on a higher-level segment for its full hierarchic meaning. A child is a dependent segment of its parent. Contrast with root segment.End of change
dependent service element (DSE)
Start of changeAn element of the active IMS system that has a counterpart in the alternate IMS system, but cannot trigger a takeover on its own. z/OS, VTAM, IRLM, and the CPC are DSEs. A DSE depends on IMS to recognize a failure in its processing and request that the alternate take over its operation.End of change
dependent table
A table that is a dependent in at least one referential constraint.
descendent
An object that is a dependent of an object or is the dependent of a descendent of an object.
descendent row
A row that is dependent on another row, or a row that is a descendent of a dependent row.
descendent table
A table that is a dependent of another table, or a table that is a descendent of a dependent table.
descriptor
A skeleton from which an IMS control block is dynamically built. A user descriptor can provide user options and queue names.
destination
Start of changeIn IMS TM, an application program, a logical terminal, or an operator command that is associated with the control region.End of change
destination parent
Start of changeIn a database, the physical or logical parent that is reached by the logical child path.End of change
destination system
In an IMS multisystem environment, the system in which the logical destination resides.
deterministic function
Start of changeA user-defined function whose result is dependent on the values of the input arguments. That is, successive invocations with the same input values produce the same answer. Sometimes referred to as a not-variant function. Contrast with nondeterministic function (sometimes called a variant function).End of change
Start of changedevice characteristics table (DCT)End of change
Start of changeAn MFS table that is generated for IBM 3270 or SLU type 2 devices with symbolic names. An entry is generated for each symbolic name and its associated screen size and physical terminal features. Different combinations of features for the same symbolic name cause separate entries in the table to be created.End of change
device field (DFLD)
Start of changeIn MFS, the smallest area in a device input format (DIF) or device output format (DOF) whose content and structure are defined by the user.End of change
device input format (DIF)
Start of changeThe MFS control block that describes the format of the data that is entered on the device and presented to MFS.End of change
device output format (DOF)
Start of changeThe MFS control block that describes the format of the output data that is presented to the device. End of change
device page (DPAGE)
In MFS, a user-defined group of device field definitions that comprise one or more physical pages to be presented to or received from the device.
DFLD
See device field.
DIF
See device input format.
dimension
A data category such as time, products, or markets. The elements of a dimension are referred to as members. See also dimension table.
dimension table
The representation of a dimension in a star schema. Each row in a dimension table represents all of the attributes for a particular member of the dimension. See also dimension, star schema, and star join.
direct dependent segment
Start of changeIn a DEDB, a segment that is chained from a root segment. A direct dependent segment is stored in either the root addressable portion or the overflow portion of a DEDB area.End of change
directory
The DB2 system database that contains internal objects such as database descriptors and skeleton cursor tables.
directory entry name
A means of identifying the directory entry of a named object to the coupling facility. The directory, all of its entries, and all of the objects associated with those entries are contained in a single structure.
disk
A direct-access storage device that records data magnetically.
distinct type
Start of changeA user-defined data type that is represented as an existing type (its source type), but is considered to be a separate and incompatible type for semantic purposes.End of change
distributed data
Data that resides on a DBMS other than the local system.
distributed data facility (DDF)
A set of DB2 components through which DB2 communicates with another relational database management system.
distributed presentation management (DPM)
An MFS option that allows programs to communicate with device independence by sharing message formatting functions between MFS and a user-written remote program. The user-written remote program performs device-dependent formatting.
distributed recovery
Resource recovery in which the resources and participants reside on multiple systems.
Distributed Relational Database Architecture (DRDA)
A connection protocol for distributed relational database processing that is used by IBM relational database products. DRDA includes protocols for communication between an application and a remote relational database management system, and for communication between relational database management systems. See also DRDA access.
DL/I
See Data Language/I.
DL/I address space
Start of changeAn address space that is used by the online IMS control program to contain most of the DL/I code and control blocks. This option can be selected for the online IMS environment to provide an alternative virtual storage configuration.End of change
DLT
See database-level tracker.
DMB
See data management block.
DNS
See domain name server.
Start of changeDOCIDEnd of change
Start of changeSee document ID.End of change
Start of changedocument IDEnd of change
Start of changeA value that uniquely identifies a row that contains an XML column. This value is stored with the row and never changes. End of change
DOF
See device output format.
domain
The set of valid values for an attribute.
domain name
The name by which TCP/IP applications refer to a TCP/IP host within a TCP/IP network.
domain name server (DNS)
A special TCP/IP network server that manages a distributed directory that is used to map TCP/IP host names to IP addresses.
double-byte character large object (DBCLOB)
Start of changeA graphic string data type in which a sequence of bytes represent double-byte characters that range in size from 0 bytes to 2 GB, less 1 byte. In general, DBCLOB values are used whenever a double-byte character string might exceed the limits of the VARGRAPHIC type.End of change
double-byte character set (DBCS)
A set of characters, which are used by national languages such as Japanese and Chinese, that have more symbols than can be represented by a single byte. Each character is 2 bytes in length. Contrast with single-byte character set and multibyte character set.
double-precision floating point number
A 64-bit approximate representation of a real number.
DPAGE
See device page.
DPM
See distributed presentation management.
DPSI
See data-partitioned secondary index.
DRA
Database resource adapter
drain
The act of acquiring a locked resource by quiescing access to that object. Contrast with claim.
drain lock
A lock on a claim class that prevents a claim from occurring.
DRD
Start of changeSee dynamic resource definition. End of change
DRDA
See Distributed Relational Database Architecture.
DRDA access
An open method of accessing distributed data that you can use to connect to another database server to execute packages that were previously bound at the server location.
DSCA
See default system control area.
DSE
See dependent service element.
DSN
  • The default DB2 subsystem name.
  • The name of the TSO command processor of DB2.
  • The first three characters of DB2 module and macro names.
DSSN
See data set sequence number.
dual logging
An optional facility that produces a duplicate copy of log data.
dynamic allocation/deallocation
A function that removes the requirement to allocate IMS databases, area data sets, and certain system data sets through JCL. A data set is allocated during IMS initialization or when it is first used and is deallocated when it is no longer used (that is, closed or stopped).
dynamic backout
A process that automatically cancels all activities performed by an application program that terminates abnormally.
dynamic cursor
A named control structure that an application program uses to change the size of the result table and the order of its rows after the cursor is opened. Contrast with static cursor.
dynamic directory
See MFS dynamic directory.
dynamic dump
A dump that is issued during the execution of a program, usually under the control of that program.
dynamic node
A VTAM node created dynamically. See dynamic terminal.
Start of changedynamic resource definition (DRD)End of change
Start of changeAn IMS function that enables users to create, update, query, and delete the following IMS resources and their descriptors dynamically, without using the batch system definition or online change processes: application programs; databases; Fast Path routing codes; transactions.End of change
dynamic SQL
Start of changeSQL statements that are prepared and executed at run time. In dynamic SQL, the SQL statement is contained as a character string in a host variable or as a constant, and it is not precompiled. End of change
dynamic terminal
A terminal created through the Extended Terminal Option (ETO). This is a terminal that has not been defined within the IMS system definition, and for which no control blocks exist at IMS initialization time. See also static terminal.
dynamic user
A user created dynamically.
EA-enabled table space
A table space or index space that is enabled for extended addressability and that contains individual partitions (or pieces, for LOB table spaces) that are greater than 4 GB.
EB
See exabyte.
EBCDIC
Extended binary coded decimal interchange code. An encoding scheme that is used to represent character data in the z/OS, VM, VSE, and iSeries environments. Contrast with ASCII and Unicode.
embedded SQL
SQL statements that are coded within an application program. See static SQL.
emergency restart
A restart of IMS following an IMS or MVS failure.
EMH
See expedited message handler.
EMHQ
See expedited message handler queues.
Start of changeenabling-new-function mode* (ENFM*)End of change
Start of changeA transitional stage of the version-to-version migration process that applies to a DB2 subsystem or data sharing group that was in new-function mode (NFM) at one time. When in enabling-new-function mode*, a DB2 subsystem or data sharing group is preparing to use the new functions of the new version but cannot yet use them. A data sharing group that is in enabling-new-function mode* cannot coexist with members that are still at the prior version level. Fallback to a prior version is not supported. Contrast with compatibility mode, compatibility mode*, enabling-new-function mode, and new-function mode.End of change
Start of changeenabling-new-function mode (ENFM)End of change
Start of changeA transitional stage of the version-to-version migration process during which the DB2 subsystem or data sharing group is preparing to use the new functions of the new version. When in enabling-new-function mode, a DB2 data sharing group cannot coexist with members that are still at the prior version level. Fallback to a prior version is not supported, and new functions of the new version are not available for use in enabling-new-function mode. Contrast with compatibility mode, compatibility mode*, enabling-new-function mode*, and new-function mode. End of change
enclave
Start of changeIn Language Environment, an independent collection of routines, one of which is designated as the main routine. An enclave is similar to a program or run unit. See also WLM enclave.End of change
encoding scheme
A set of rules to represent character data (ASCII, EBCDIC, or Unicode).
end-user significant status
Start of change A type of significant status that relates to the work associated with a resource. IMS defines conversations, set-and-test-sequence numbers terminals, and Fast Path as end-user significant status for nodes and users.End of change
end-user terminal
A terminal where an IMS user can issue transactions, some commands (based upon security authorization), and message switches.
ENFM
Start of changeSee enabling-new-function mode.End of change
ENFM*
Start of changeSee enabling-new-function mode*.End of change
entity
Start of changeA person, object, or concept about which information is stored. In a relational database, entities are represented as tables. A database includes information about the entities in an organization or business, and their relationships to each other. End of change
entrykey
A key value assigned to a coupling facility list structure list entry by the originator. For example, CQS uses the client queue name for queues on a queue structure or the client resource name for resources on a resource structure.
enumerated list
A set of DB2 objects that are defined with a LISTDEF utility control statement in which pattern-matching characters (*, %;, _, or ?) are not used.
environment
A collection of names of logical and physical resources that are used to support the performance of a function.
environment handle
Start of changeA handle that identifies the global context for database access. All data that is pertinent to all objects in the environment is associated with this handle. End of change
EPST
See extended partition specification table.
EQE
See error queue element.
equijoin
A join operation in which the join-condition has the form expression = expression. See also join, full outer join, inner join, left outer join, outer join, and right outer join.
error page range
A range of pages that are considered to be physically damaged. DB2 does not allow users to access any pages that fall within this range.
error queue element (EQE)
Start of changeA piece of data that is maintained for a Fast Path area data set block that cannot be accessed. Each data set can have up to ten damaged blocks (control intervals).End of change
ESAF
See External Subsystem Attach Facility.
escape character
The symbol, a double quotation (") for example, that is used to enclose an SQL delimited identifier.
ESCD
See extended system contents directory.
ETO
See Extended Terminal Option.
ETO descriptor
A template that contains information about the physical characteristics of terminals, user options and message queue names, and remote LTERMs associated with MSC links. See also logon descriptor, MFS device descriptor, MSC descriptor, and user descriptor.
exabyte
A unit of measure for processor, real and virtual storage capacities, and channel volume that has a value of 1 152 921 504 606 846 976 bytes or 260.
exception
Start of changeAn SQL operation that involves the EXCEPT set operator, which combines two result tables. The result of an exception operation consists of all of the rows that are in only one of the result tables.End of change
exception table
A table that holds rows that violate referential constraints or check constraints that the CHECK DATA utility finds.
exclusive access
An access intent that establishes the intent of an application to reserve the exclusive use of the database. If a subsystem requests and DBRC grants exclusive access to a subsystem, then no other subsystem may access the database concurrently, regardless of the share level of the database.
exclusive lock
A lock that prevents concurrently executing application processes from reading or changing data. Contrast with share lock.
exclusive mode
An optional mode of terminal operation in which a terminal may receive no output other than a response to an input. Any output excluded from being sent is held for transmission until the terminal is removed from exclusive mode.
executable statement
An SQL statement that can be embedded in an application program, dynamically prepared and executed, or issued interactively.
execution context
In SQLJ, a Java object that can be used to control the execution of SQL statements.
exit routine
A user-written (or IBM-provided default) program that receives control from DB2 to perform specific functions. Exit routines run as extensions of DB2.
expanding conversion
A process that occurs when the length of a converted string is greater than that of the source string. For example, this process occurs when an ASCII mixed-data string that contains DBCS characters is converted to an EBCDIC mixed-data string; the converted string is longer because shift codes are added.
expedited message handler (EMH)
The IMS Fast Path facility that processes single-segment input and output messages. Fast Path messages that use the EMH bypass the normal message queuing and application scheduling and therefore these messages are processed faster than non-Fast Path messages.
expedited message handler queues (EMHQ)
The expedited message handler shared queues on a coupling facility list structure.
explicit hierarchical locking
Locking that is used to make the parent-child relationship between resources known to IRLM. This kind of locking avoids global locking overhead when no inter-DB2 interest exists on a resource.
explicit literal
In MFS, a literal field defined by the user for inclusion in an input or output message. See also default literal and system literal.
explicit privilege
Start of changeA privilege that has a name and is held as the result of an SQL GRANT statement and revoked as the result of an SQL REVOKE statement. For example, the SELECT privilege. End of change
exposed name
A correlation name or a table or view name for which a correlation name is not specified.
express alternate PCB
An alternate PCB to which output messages are sent before termination of the application program.
expression
An operand or a collection of operators and operands that yields a single value.
extended checkpoint/restart
The facility that allows batch processing programs to establish database positioning and initiate user-specified areas with a DL/I call in place of an OS CHKPT macro.
extended partition specification table (EPST)
For Fast Path, an extension of the PST. It contains information for a dependent region that is unique to Fast Path.
extended pointer set (EPS)
In a HALDB, an expanded segment prefix that includes information that allows the use of indirect pointers. An EPS is created for logical child segments and secondary index segments.
Extended Recovery Facility (XRF)
For DB2 A facility that minimizes the effect of failures in z/OS, VTAM, the host processor, or high-availability applications during sessions between high-availability applications and designated terminals. This facility provides an alternative subsystem to take over sessions from the failing subsystem.
For IMS A function of IMS that minimizes the impact of IMS failures by having an alternate IMS monitor an active IMS and take over production if the active IMS fails.
extended restart
A restart, initiated by a DL/I call, that reestablishes database positioning and user-specified areas.
extended system contents directory (ESCD)
An extension of SCD that is used for Fast Path.
Extended Terminal Option (ETO)
Start of changeA feature of IMS Transaction Manager that enables users to add or delete ACF/VTAM terminals or message queues (LTERMs) dynamically.End of change
Extensible Markup Language (XML)
A standard metalanguage for defining markup languages that is a subset of Standardized General Markup Language (SGML).
external function
Start of changeA function that has its functional logic implemented in a programming language application that resides outside the database, in the file system of the database server. The association of the function with the external code application is specified by the EXTERNAL clause in the CREATE FUNCTION statement. External functions can be classified as external scalar functions and external table functions. Contrast with sourced function, built-in function, and SQL function.End of change
external procedure
Start of changeA procedure that has its procedural logic implemented in an external programming language application. The association of the procedure with the external application is specified by a CREATE PROCEDURE statement with a LANGUAGE clause that has a value other than SQL and an EXTERNAL clause that implicitly or explicitly specifies the name of the external application. Contrast with external SQL procedure and native SQL procedure.End of change
external routine
A user-defined function or stored procedure that is based on code that is written in an external programming language.
Start of changeexternal SQL procedureEnd of change
Start of changeAn SQL procedure that is processed using a generated C program that is a representation of the procedure. When an external SQL procedure is called, the C program representation of the procedure is executed in a stored procedures address space. Contrast with external procedure and native SQL procedure. End of change
external subsystem
A subsystem that provides a set of resources to be used by IMS, but not controlled by it.
External Subsystem Attach Facility (ESAF)
A facility that allows applications running under IMS to obtain data from external subsystems, such as DB2.
failed member state
A state of a member of a data sharing group in which the member's task, address space, or z/OS system terminates before the state changes from active to quiesced.
fallback
Start of changeThe process of returning to a previous release of DB2 after attempting or completing migration to a current release. Fallback is supported only from a subsystem that is in compatibility mode. End of change
false global lock contention
A contention indication from the coupling facility that occurs when multiple lock names are hashed to the same indicator and when no real contention exists.
fan set
Start of changeA direct physical access path to data, which is provided by an index, hash, or link; a fan set is the means by which DB2 supports the ordering of data. End of change
Fast Database Recovery (FDBR) region
A separate IMS control region that monitors IMS, detects failure, and recovers any database resources that are locked by the failed IMS, making them available for other IMSs.
Fast Path
IMS functions for applications that require good response characteristics and that may have large transaction volumes. Programs have rapid access to main-storage databases (to the field level), and to direct-access data entry databases. Message processing is grouped for load balancing and synchronized for database integrity and recovery. See also main storage database, data entry database, and load balancing group.
Fast Path databases
Two types of databases designed to provide high data availability and fast processing for IMS applications. They can be processed by all types of application programs. See also main storage database and data entry database.
Fast Path dependent region
See IMS Fast Path region.
Fast Path exclusive transaction
A transaction type whose messages are routed to EMH for processing. See also Fast Path potential transaction.
Fast Path potential transaction
A transaction type that can be routed to either EMH or TM processing. See also Fast Path exclusive transaction.
Start of changefast replication image copyEnd of change
Start of changeA type of image copy that is taken by the Database Image Copy 2 utility by using the DFSMS fast replication option and either the FlashCopy function of the Enterprise Storage Server (ESS) hardware or the SnapShot copy function of the RAMAC Virtual Array (RVA).End of change
FDBR
See Fast Database Recovery (FDBR) region.
federated database
The combination of a DB2 server (in Linux, UNIX, and Windows environments) and multiple data sources to which the server sends queries. In a federated database system, a client application can use a single SQL statement to join data that is distributed across multiple database management systems and can view the data as if it were local.
fetch orientation
Start of changeThe specification of the desired placement of the cursor as part of a FETCH statement. The specification can be before or after the rows of the result table (with BEFORE or AFTER). The specification can also have either a single-row fetch orientation (for example, NEXT, LAST, or ABSOLUTE n) or a rowset fetch orientation (for example, NEXT ROWSET, LAST ROWSET, or ROWSET STARTING AT ABSOLUTE n).End of change
field
In a database, a portion (as defined during DBDGEN) within a segment that is the smallest unit of the data that can be referred to. See also key field.
field-level sensitivity
The ability of an application program to access data at the field level. See sensitivity.
field procedure
A user-written exit routine that is designed to receive a single value and transform (encode or decode) it in any way the user can specify.
field search argument (FSA)
For Fast Path, the I/O area that is constructed by an application program to identify a field within a segment that is to be processed with a FLD call.
field tab (FTAB)
In MFS, a character defined for operator use in separating input fields if the length of the entered data is less than the defined field length, or there is no data for a field.
Start of changefile reference variableEnd of change
Start of changeA host variable that is declared with one of the derived data types (BLOB_FILE, CLOB_FILE, DBCLOB_FILE); file reference variables direct the reading of a LOB from a file or the writing of a LOB into a file.End of change
fill characters
In MFS, the characters used to pad input message fields or output device fields when the length of the received data is less than the length defined for the field or no data is received for the field.
filter factor
A number between zero and one that estimates the proportion of rows in a table for which a predicate is true.
FINDDEST
See Find Destination.
Find Destination (FINDDEST)
Find Destination is an internal service in IMS used for finding certain IMS resources (CCB, CVB, SMB, CNT, RCNT, LNB, and QAB), most of which represent IMS destinations. For searches other than CVBs and CCBs, if the block is not found, then if requested, a search for an LU 6.2 descriptor is made. If LU 6.2 is not requested, or the search fails, then if ETO is active and the caller of FINDDEST request creation, a call is made to create a new user structure for the given destination name.
fixed-length string
Start of changeA character, graphic, or binary string whose length is specified and cannot be changed. Contrast with varying-length string.End of change
FlashCopy
Start of changeA function on the IBM Enterprise Storage Server that can, in conjunction with the BACKUP SYSTEM utility, create a point-in-time copy of data while an application is running. End of change
foreign key
A column or set of columns in a dependent table of a constraint relationship. The key must have the same number of columns, with the same descriptions, as the primary key of the parent table. Each foreign key value must either match a parent key value in the related parent table or be null.
forest
An ordered set of subtrees of XML nodes.
format set
In MFS, a format definition, all message definitions that refer to the format definition, and any table referred to by the format.
forward log recovery
The third phase of restart processing during which DB2 processes the log in a forward direction to apply all REDO log records.
free space
The total amount of unused space in a page; that is, the space that is not used to store records or control information is free space.
free space element anchor point (FSEAP)
Start of changeIn a hierarchical direct database, the first four bytes of a CI or block. The first 2-byte field contains the offset, in bytes, to the first FSE in the CI or block. The second 2-byte field identifies whether this block or CI contains a bit map.End of change
free space element (FSE)
In a hierarchical direct database, the first 8 bytes of an area that is free space. The FSE describes the area of free space in a CI or block that is 8 or more bytes in length.
front-end system
An IMS in an MSC network in which all terminals are connected, messages are routed to the proper processing IMS, and all replies are routed to the terminals. A front-end system may also perform back-end processing. See also back-end system, pseudo-front-end system, and transaction processing system.
FSA
See field search argument.
FTAB
See field tab.
full-function database
Hierarchic database that is accessed through Data Language I (DL/I) call language and can be processed by all six types of application programs: IFP, MPP, BMP, JMP, JBP, and batch. Full-function databases include HDAM, PHDAM, HIDAM, PHIDAM, HSAM, HISAM, SHSAM, and SHISAM.
full outer join
The result of a join operation that includes the matched rows of both tables that are being joined and preserves the unmatched rows of both tables. See also join, equijoin, inner join, left outer join, outer join, and right outer join.
Start of changefullselectEnd of change
Start of changeA subselect, a fullselect in parentheses, or a number of both that are combined by set operators. Fullselect specifies a result table. If a set operator is not used, the result of the fullselect is the result of the specified subselect or fullselect.End of change
fully escaped mapping
A mapping from an SQL identifier to an XML name when the SQL identifier is a column name.
function
A mapping, which is embodied as a program (the function body) that is invocable by means of zero or more input values (arguments) to a single value (the result). See also aggregate function and scalar function.

Functions can be user-defined, built-in, or generated by DB2. (See also built-in function, cast function, external function, sourced function, SQL function, and user-defined function.)

function definer
The authorization ID of the owner of the schema of the function that is specified in the CREATE FUNCTION statement.
function package
A package that results from binding the DBRM for a function program.
function package owner
The authorization ID of the user who binds the function program's DBRM into a function package.
function signature
The logical concatenation of a fully qualified function name with the data types of all of its parameters.
fuzzy image copy
An image copy of an online database. The database can be updated while the image copy is being taken and some, all, or none of the updates might appear in the image copy. Also called concurrent image copy.
gap
Active-site log data that is not available to the tracking IMS. The log data might be missing either because it was not sent or because an I/O error occurred at the tracking site.
GB
Gigabyte. A value of (1 073 741 824 bytes).
GBP
See group buffer pool.
GBP-dependent
The status of a page set or page set partition that is dependent on the group buffer pool. Either read/write interest is active among DB2 subsystems for this page set, or the page set has changed pages in the group buffer pool that have not yet been cast out to disk.
Generalized Sequential Access Method (GSAM)
A database access method providing accessing support for simple physical sequential data sets, such as tape files, SYSIN, SYSOUT, and other files that are not hierarchic in nature. Available only in BMP and Batch.
Generalized Sequential Access Method program communication block (GSAM PCB)
The PCB that describes an application program's interface to a GSAM data set. One GSAM PCB is required for each GSAM data set view used by the application program.
generalized trace facility (GTF)
A z/OS service program that records significant system events such as I/O interrupts, SVC interrupts, program interrupts, or external interrupts.
generic resource group
A set of IMS systems that have the same generic resource name, enabling VTAM to distribute terminal sessions among them.
generic resource member
An IMS system that belongs to a generic resource group.
generic resource name
A name that VTAM uses to represent several application programs that provide the same function in order to handle session distribution and balancing in a Sysplex environment.
Start of changegeographic featureEnd of change
Start of changeAn object on the surface of the Earth (such as a city or river), a space (such as a safety zone around a hazardous site), or an event that occurs at a location (such as an auto accident that occurred at a particular intersection).End of change
Start of changegeographic information systemEnd of change
Start of changeA complex of objects, data, and applications that is used to create and analyze spatial information about geographic features.End of change
getpage
An operation in which DB2 accesses a data page.
global lock
For DB2 A lock that provides concurrency control within and among DB2 subsystems. The scope of the lock is across all DB2 subsystems of a data sharing group.
For IMS An IRLM lock that interests two IRLMs; both must coordinate to grant it.
global lock contention
Conflicts on locking requests between different DB2 members of a data sharing group when those members are trying to serialize shared resources.
global lock management
Lock management that controls access to resources shared among IMS systems participating in block level sharing.
global online change
An IMS function that changes resources online for all IMSs in an IMSplex.
global service group
The collection of all IMS subsystems that can access a particular set of databases. A global service group can span several MVS systems at more than one geographical location.
governor
See resource limit facility.
graphic string
Start of changeA sequence of DBCS characters. Graphic data can be further classified as GRAPHIC, VARGRAPHIC, or DBCLOB.End of change
Start of changeGRECPEnd of change
Start of changeSee group buffer pool recovery pending.End of change
gross lock
The shared, update, or exclusive mode locks on a table, partition, or table space.
group buffer pool duplexing
The ability to write data to two instances of a group buffer pool structure: a primary group buffer pool and a secondary group buffer pool. z/OS publications refer to these instances as the "old" (for primary) and "new" (for secondary) structures.
group buffer pool (GBP)
A coupling facility cache structure that is used by a data sharing group to cache data and to ensure that the data is consistent for all members.
Start of changegroup buffer pool recovery pending (GRECP)End of change
Start of changeThe state that exists after the buffer pool for a data sharing group is lost. When a page set is in this state, changes that are recorded in the log must be applied to the affected page set before the page set can be used.End of change
group level
The release level of a data sharing group, which is established when the first member migrates to a new release.
group member
The name of an entity that joins an XCF group and communicates with IMS using the OTMA protocol. A member can be either a server (IMS) or a client.
group name
The z/OS XCF identifier for a data sharing group.
group restart
A restart of at least one member of a data sharing group after the loss of either locks or the shared communications area.
GSAM
See Generalized Sequential Access Method.
GSAM PCB
See Generalized Sequential Access Method program communication block.
GSG
See global service group.
GTF
Start of changeSee generalized trace facility. End of change
HALDB
See High Availability Large Database.
HALDB master
A named entity of a High Availability Large Database that represents only the structural definition of data and refers to the entire collection of partitions.
HALDB OLR
See HALDB Online Reorganization.
HALDB Online Reorganization (HALDB OLR)
A function of IMS that allows non-disruptive, online reorganization of PHDAM and PHIDAM partitions.
HALDB partition
A named entity of a High Availability Large Database that represents a partition of a HALDB.
handle
In DB2 ODBC, a variable that refers to a data structure and associated resources. See also statement handle, connection handle, and environment handle.
help panel
A screen of information that presents tutorial text to assist a user at the workstation or terminal.
heuristic damage
The inconsistency in data between one or more participants that results when a heuristic decision to resolve an indoubt LUW at one or more participants differs from the decision that is recorded at the coordinator.
heuristic decision
A decision that forces indoubt resolution at a participant by means other than automatic resynchronization between coordinator and participant.
Hierarchical Direct Access Method (HDAM)
A database access method using algorithmic addressability to records in a hierarchic direct organization. A choice of OSAM or VSAM ESDS is available as a base for HDAM.
Hierarchical Indexed Direct Access Method (HIDAM)
A database access method used for indexed access to records in a hierarchic direct organization. It provides indexed access to the root segments and pointer access to subordinate segments.
Hierarchical Indexed Sequential Access Method (HISAM)
A database access method used for indexed access to records in a hierarchic sequential organization.
Hierarchical Sequential Access Method (HSAM)
An IMS HS organization that is used for sequential storage and access of segments on tape or direct access storage. BSAM and QSAM are used as the basis for HSAM.
hierarchic direct (HD) organization
The physical storage organization in which database segments that represent a physical database record are related by direct address pointers in the segment's prefix.
hierarchic sequence
In a database, the sequence of segment occurrences in a database record defined by traversing the tree top to bottom, front to back, and left to right.
hierarchic sequential (HS) organization
The physical storage organization in which database segments that represent a physical database record are related by adjacency.
hierarchy
The tree-like arrangement of segments in a database, beginning with the root segment and proceeding down to dependent segments.
High Availability Large Database (HALDB)
A partitioned full-function DL/I database. The supported database organizations are PHDAM, PHIDAM, and PSINDEX.
high-speed sequential processing (HSSP)
An option, available only to batch message programs, for optimizing the sequential processing of DEDB areas. A simultaneous image copy can also be created.
Start of changehistogram statisticsEnd of change
Start of changeA way of summarizing data distribution. This technique divides up the range of possible values in a data set into intervals, such that each interval contains approximately the same percentage of the values. A set of statistics are collected for each interval.End of change
hole
A row of the result table that cannot be accessed because of a delete or an update that has been performed on the row. See also delete hole and update hole.
home address space
The area of storage that z/OS currently recognizes as dispatched.
host
The set of programs and resources that are available on a given TCP/IP instance.
host expression
A Java variable or expression that is referenced by SQL clauses in an SQLJ application program.
host identifier
A name that is declared in the host program.
host language
A programming language in which you can embed SQL statements.
host program
An application program that is written in a host language and that contains embedded SQL statements.
host structure
In an application program, a structure that is referenced by embedded SQL statements.
host variable
Start of changeIn an application program written in a host language, an application variable that is referenced by embedded SQL statements. End of change
host variable array
An array of elements, each of which corresponds to a value for a column. The dimension of the array determines the maximum number of rows for which the array can be used.
HSSP
See high-speed sequential processing.
IBM System z9 Integrated Processor (zIIP)
Start of changeA specialized processor that can be used for some DB2 functions.End of change
IC
See image copy.
IDCAMS
An IBM program that is used to process access method services commands. It can be invoked as a job or jobstep, from a TSO terminal, or from within a user's application program.
IDCAMS LISTCAT
A facility for obtaining information that is contained in the access method services catalog.
identity column
Start of changeA column that provides a way for DB2 to automatically generate a numeric value for each row. Identity columns are defined with the AS IDENTITY clause. Uniqueness of values can be ensured by defining a unique index that contains only the identity column. A table can have no more than one identity column.End of change
IFCID
See instrumentation facility component identifier.
IFI
See instrumentation facility interface.
IFI call
An invocation of the instrumentation facility interface (IFI) by means of one of its defined functions.
IFP
IMS Fast Path program, a type of program designed to operate with expedited message handling (EMH) in a Fast Path region.
ILDS
See indirect list data set.
ILE
See indirect list entry.
ILK
See indirect list entry key.
ILS
See isolated log sender.
image copy
For DB2 An exact reproduction of all or part of a table space. DB2 provides utility programs to make full image copies (to copy the entire table space) or incremental image copies (to copy only those pages that have been modified since the last image copy).
For IMS The process of creating a backup of a DBDS. The backup data set created by the image copy process. See also fuzzy image copy.
immediate checkpoint
The facility that writes simple checkpoint information without requiring termination of MPPs.
IMS
Information Management System. Any of several system environments available with Database Manager and Transaction Manager, capable of managing complex databases and terminal networks.
IMS attachment facility
A DB2 subcomponent that uses z/OS subsystem interface (SSI) protocols and cross-memory linkage to process requests from IMS to DB2 and to coordinate resource commitment.
IMS Command Center
A component of the Control Center that is used to easily issue IMS commands from a workstation to multiple IMS systems.
Start of changeIMS control programEnd of change
The IMS program that initiates and controls the major IMS facilities, such as IMS database, telecommunications, and message scheduling.
Start of changeIMS Database Manager (IMS DB)End of change
Start of changeThe IMS Database Manager licensed program, which processes concurrent database calls and offers high performance for a variety of applications.End of change
IMS Fast Path region
An online environment in which message-driven programs and DEDB online utilities operate.
IMS generic resource name
The name by which IMS systems in a generic resource group are known to VTAM.
IMSID
The 4-byte subsystem identification used by a given IMS job. For the shared-queues and data-sharing environment, the IMSID must be unique; in other cases, the IMSID does not need to be unique.
IMS instance
An active, unique IMS system in an IMSplex.
Start of changeIMS JDBC driverEnd of change
Start of changeA driver that provides a connection to the IMS database, which enables users to access and change the database by using SQL queries.End of change
IMS Monitor
An optional IMS facility that records the activity of the IMS control region and dependent regions.
IMSplex
One or more IMSs that work together as a unit. Typically these IMSs share resources, run in a Parallel Sysplex environment, and include a CSL.
IMSplex component
An entity (typically running in its own address space) that manages resources, operations, or facilitates communications between other IMS-defined entities. Examples of IMSplex components are IMS subsystems (DB/DC, DBCTL, DCCTL), the Resource Manager, the Operations Manager, and the Structured Call Interface. A DLIBATCH or DBBBATCH region is considered a IMSplex component even though it does not interact with the Common Service Layer managers.
IMSplex member
Any IMS-defined entity in an IMSplex that typically runs in its own address space and is managed by the IMS Common Service Layer.
IMS subsystem
See IMS system.
IMS system
The IMS control region and its associated separate address spaces (DL/I and DBRC) and dependent regions.
IMS system log
Logically, a single log made up of online data sets (OLDSs) and write-ahead data sets (WADSs).
Start of changeIMS Transaction Manager (IMS TM)End of change
Start of changeThe IMS Transaction Manager licensed program, a data communication system that provides high-volume, high-performance, high-capacity, low-cost transaction processing for both IMS Database Manager (IMS DB) and DB2 databases. End of change
in-abort
A status of a unit of recovery. If DB2 fails after a unit of recovery begins to be rolled back, but before the process is completed, DB2 continues to back out the changes during restart.
inactive libraries
Those libraries not currently in use by the online IMS system in a system using online change. These libraries may be at a different level than the current or active libraries.
in-commit
A status of a unit of recovery. If DB2 fails after beginning its phase 2 commit processing, it "knows," when restarted, that changes made to data are consistent. Such units of recovery are termed in-commit.
independent
An object (row, table, or table space) that is neither a parent nor a dependent of another object.
index
A set of pointers that are logically ordered by the values of a key. Indexes can provide faster access to data and can enforce uniqueness on the rows in a table.
index-controlled partitioning
A type of partitioning in which partition boundaries for a partitioned table are controlled by values that are specified on the CREATE INDEX statement. Partition limits are saved in the LIMITKEY column of the SYSIBM.SYSINDEXPART catalog table.
indexed segment
In a database, a segment that is located by an index and termed an index target segment.
indexing segment
The segment in an index database that contains a pointer to a segment containing data (the indexed segment), and termed an index pointer segment.
index key
The set of columns in a table that is used to determine the order of index entries.
index partition
A VSAM data set that is contained within a partitioning index space.
index pointer segment
In a secondary index, the segment that contains the data and pointers used to index the index target segments.
index source segment
In a database, the segment containing the data from which the indexing segment is built. It can be the same as the indexed segment or one of its dependents.
index space
A page set that is used to store the entries of one index.
index target segment
In a database, the segment pointed to by a secondary index entry, that is, from an index pointer segment.
indicator column
A 4-byte value that is stored in a base table in place of a LOB column.
indicator variable
A variable that is used to represent the null value in an application program. If the value for the selected column is null, a negative value is placed in the indicator variable.
indirect list data set (ILDS)
In a HALDB, an IMS system index data set. The ILDS is a repository for the indirect pointers used for PHDAM and PHIDAM databases. There is one ILDS per partition in PHDAM or PHIDAM databases.
indirect list entry (ILE)
In a HALDB, an entry in an indirect list data set.
indirect list entry key (ILK)
In a HALDB, a unique token that is assigned to a segment in PHDAM and PHIDAM databases when the segment is created. Eight bytes in length and stored in the prefix of the segment, the ILK uniquely identifies every segment in PHDAM and PHIDAM databases.
indirect pointer
In a HALDB, a pointer stored in the indirect list data set and used to eliminate the need to update pointers throughout other database records when a single partition is reorganized. Indirect pointers are stored in an Indirect List Data Set.
indoubt
Start of changeA status of a unit of recovery. If DB2 fails after it has finished its phase 1 commit processing and before it has started phase 2, only the commit coordinator knows if an individual unit of recovery is to be committed or rolled back. At restart, if DB2 lacks the information it needs to make this decision, the status of the unit of recovery is indoubt until DB2 obtains this information from the coordinator. More than one unit of recovery can be indoubt at restart.End of change
indoubt resolution
The process of resolving the status of an indoubt logical unit of work to either the committed or the rollback state.
indoubt unit of work
A transaction or database update that has been prepared for commit, but is not yet committed. If a failure occurs before the indoubt unit of work is committed, IMS must resolve all the work whose status is in doubt.
inflight
For DB2 A status of a unit of recovery. If DB2 fails before its unit of recovery completes phase 1 of the commit process, it merely backs out the updates of its unit of recovery at restart. These units of recovery are termed inflight.
For IMS The state of a resource or unit of recovery that has not yet completed the prepare phase of the commit process.
inheritance
The passing downstream of class resources or attributes from a parent class in the class hierarchy to a child class.
initialization file
For DB2 ODBC applications, a file containing values that can be set to adjust the performance of the database manager.
inline copy
A copy that is produced by the LOAD or REORG utility. The data set that the inline copy produces is logically equivalent to a full image copy that is produced by running the COPY utility with read-only access (SHRLEVEL REFERENCE).
inner join
The result of a join operation that includes only the matched rows of both tables that are being joined. See also join, equijoin, full outer join, left outer join, outer join, and right outer join.
inoperative package
A package that cannot be used because one or more user-defined functions or procedures that the package depends on were dropped. Such a package must be explicitly rebound. Contrast with invalid package.
input message
Any valid command, transaction, or message switch.
input mode
In MFS, the way in which input fields from certain devices are defined by the user to be scanned by MFS. See also record mode and stream mode.
Start of changeinput output area input (IOAI)End of change
Start of changeAn I/O area that is used by the Fast Path DL/I calls that return structural information about DEDBs.End of change
input/output program communication block (I/O PCB)
A TP PCB provided automatically by IMS to an application program that executes in a communication system with TM. The I/O PCB is the mechanism by which a program obtains an input message from a terminal and returns a reply to the terminal that originated the input message. See also alternate program communication block.
input system
In an MSC network, the system to which the input terminal is attached.
input terminal
In an MSC network, the terminal from which a primary request originated.
inquiry logical terminal
A type of logical terminal that is created automatically by IMS and restricted to non-update transactions. Inquiry logical terminals are created for non-VTAM switched lines. See also logical terminal.
insensitive cursor
A cursor that is not sensitive to inserts, updates, or deletes that are made to the underlying rows of a result table after the result table has been materialized.
insert trigger
Start of changeA trigger that is defined with the triggering SQL operation, an insert.End of change
install
The process of preparing a DB2 subsystem to operate as a z/OS subsystem.
Start of changeinstallation verification program (IVP)End of change
Start of changeA procedure that is integral to the IMS installation process, and that tests the newly-installed IMS system to verify that the basic facilities of IMS are functioning properly. The jobs and tasks of the IVP also build a sample IMS system and provide several sample applications that are used to verify specific components of IMS.End of change
Start of changeINSTEAD OF triggerEnd of change
Start of changeA trigger that is associated with a single view and is activated by an insert, update, or delete operation on the view and that can define how to propagate the insert, update, or delete operation on the view to the underlying tables of the view. Contrast with BEFORE trigger and AFTER trigger.End of change
instrumentation facility component identifier (IFCID)
A value that names and identifies a trace record of an event that can be traced. As a parameter on the START TRACE and MODIFY TRACE commands, it specifies that the corresponding event is to be traced.
instrumentation facility interface (IFI)
A programming interface that enables programs to obtain online trace data about DB2, to submit DB2 commands, and to pass data to DB2.
intelligent remote station support (IRSS)
The IMS facility that supports the IBM System/3 and IBM System/7.
intent propagation
A condition handled internally by IMS by which processing intent for one segment can propagate to related segments depending on the type of processing and the kind of relationship. It determines the compatibility of scheduling processing applications in parallel or serially.
interactive dump formatter
An enhancement to the IMS offline dump formatter that allows you to format your IMS dumps through a series of interactive menu-driven panels rather than by creating or editing a DFSFRMAT data set.
Interactive System Productivity Facility (ISPF)
An IBM licensed program that provides interactive dialog services in a z/OS environment.
inter-DB2 R/W interest
A property of data in a table space, index, or partition that has been opened by more than one member of a data sharing group and that has been opened for writing by at least one of those members.
intermediate database server
The target of a request from a local application or a remote application requester that is forwarded to another database server.
intermediate system
In an MSC network, a system through which a message passes on its way from the input system to the destination system, or vice-versa, in which no processing other than routing is performed.
internal resource lock manager (IRLM)
For DB2 A z/OS subsystem that DB2 uses to control communication and database locking.
Start of changeFor IMS A subsystem in a z/OS environment that provides lock management, and is used by IMSs to share data.End of change
internationalization
The support for an encoding scheme that is able to represent the code points of characters from many different geographies and languages. To support all geographies, the Unicode standard requires more than 1 byte to represent a single character. See also Unicode.
Start of changeintersectionEnd of change
Start of changeAn SQL operation that involves the INTERSECT set operator, which combines two result tables. The result of an intersection operation consists of all of the rows that are in both result tables.End of change
intersection data
Any user data in a logical child segment that does not include the logical parent's concatenated key.
Intersystem Communication (ISC)
Start of changeAn extension of IMS Multiple Systems Coupling (MSC) that permits the connection of IMS to another IMS subsystem, to CICS on z/OS, or to a user-written subsystem, as long as both subsystems use ISC. Also known as LU 6.1.End of change
invalid package
A package that depends on an object (other than a user-defined function) that is dropped. Such a package is implicitly rebound on invocation. Contrast with inoperative package.
Start of changeIOAIEnd of change
Start of changeSee input/output program communication block.End of change
I/O PCB
See input/output program communication block.
I/O prevention
The z/OS process that, during an XRF takeover, ensures that the failing active IMS cannot change the databases during the takeover.
I/O toleration
The IMS process that, during an XRF takeover, allows transaction processing after a takeover before I/O prevention has completed.
IP address
Start of changeA value that uniquely identifies a TCP/IP host. End of change
IRLM
See internal resource lock manager.
IRLM session
An IRLM may have two kinds of VTAM sessions with another IRLM: a primary session and a secondary session (also called an alternate session).
IRSS
See intelligent remote station support.
ISC
See Intersystem Communication.
ISC static user
An ISC user defined using the SUBPOOL macro in an IMS system definition.
Start of changeisolated log sender (ILS)End of change
In an RSR environment, a component of the Transport Manager Subsystem that sends gap data to the tracking subsystem.
isolation level
The degree to which a unit of work is isolated from the updating operations of other units of work. See also cursor stability, read stability, repeatable read, and uncommitted read.
ISPF
See Interactive System Productivity Facility.
iterator
In SQLJ, an object that contains the result set of a query. An iterator is equivalent to a cursor in other host languages.
iterator declaration clause
In SQLJ, a statement that generates an iterator declaration class. An iterator is an object of an iterator declaration class.
IVP
See installation verification procedure.
JAR
See Java Archive.
Java Archive (JAR)
A file format that is used for aggregating many files into a single file.
Java batch processing (JBP) region
An IMS dependent region with a persistent JVM that allows the scheduling of online non-message-driven batch Java applications, similar to a BMP.
Start of changeJava class libraries for IMSEnd of change
Start of changeA Java library that allows JDBC access to IMS databases from JMP or JBP applications, WebSphere Application Server for z/OS Enterprise JavaBeans (EJBs), CICS JCICS applications, and DB2 for z/OS stored procedures. End of change
Java message processing (JMP) region
An IMS dependent region with a persistent JVM that allows the scheduling of message-driven Java applications, similar to a MPP.
JDBC
A Sun Microsystems database application programming interface (API) for Java that allows programs to access database management systems by using callable SQL.
join
A relational operation that allows retrieval of data from two or more tables based on matching column values. See also equijoin, full outer join, inner join, left outer join, outer join, and right outer join.
KB
Kilobyte. A value of 1024 bytes.
Kerberos
A network authentication protocol that is designed to provide strong authentication for client/server applications by using secret-key cryptography.
Kerberos ticket
A transparent application mechanism that transmits the identity of an initiating principal to its target. A simple ticket contains the principal's identity, a session key, a timestamp, and other information, which is sealed using the target's secret key.
key
Start of changeA column, an ordered collection of columns, or an expression that is identified in the description of a table, index, or referential constraint. The same column or expression can be part of more than one key.End of change
key field
The field in a database segment used to store segment occurrences in sequential ascending order. A key field is also a search field. See also search field.
key-sequenced data set (KSDS)
A VSAM file or data set whose records are loaded in key sequence and controlled by an index.
KSDS
Start of changeSee key-sequenced data set. End of change
large object (LOB)
A sequence of bytes representing bit data, single-byte characters, double-byte characters, or a mixture of single- and double-byte characters. A LOB can be up to 2 GB minus 1 byte in length. See also binary large object, character large object, and double-byte character large object.
last agent optimization
An optimized commit flow for either presumed-nothing or presumed-abort protocols in which the last agent, or final participant, becomes the commit coordinator. This flow saves at least one message.
latch
Start of changeFor DB2 A DB2 mechanism for controlling concurrent events or the use of system resources. End of change
Start of changeFor IMS A programming device that provides short-term serialization for IMS tasks that are running in the online IMS system. Similar in function to a z/OS lock.End of change
LCID
See log control interval definition.
LDS
See linear data set.
leaf page
Start of changeAn index page that contains pairs of keys and RIDs and that points to actual data. Contrast with nonleaf page. End of change
left outer join
The result of a join operation that includes the matched rows of both tables that are being joined, and that preserves the unmatched rows of the first table. See also join, equijoin, full outer join, inner join, outer join, and right outer join.
level
In a database, the successive vertical dependencies in a hierarchic structure.
level one data sharing
Also called database level sharing and area level sharing. For DEDB areas, DBRC may authorize only one subsystem to update the database and multiple subsystems that do not need to be protected from incomplete changes made by the updater to read it, or it may authorize multiple subsystems to read the database. For area level sharing, DBRC may authorize the update or read of an area.
level three data sharing
Also called interprocessor block level sharing. DBRC and one IRLM and VTAM on each MVS system may concurrently authorize and protect multiple subsystems on different MVS systems for updating or reading the database. The IRLMs may reside in one or more z/OS operating system images.
level two data sharing
Also called intraprocessor block level sharing. DBRC and one IRLM may concurrently authorize and protect multiple subsystems on the same MVS system for updating or reading the database.
level zero data sharing
Also called exclusive level sharing. The level of data sharing in which DBRC allows only one subsystem (for example, one online IMS) to access the database.
limit count
The number that determines whether the normal or limit priority value is assigned to a transaction during the scheduling process. See also normal priority and limit priority.
limit key
The highest value of the index key for a partition.
limit priority
The priority to which a transaction is raised when the number of transactions enqueued and waiting to be processed is equal to or greater than the limit count value. See also normal priority and limit count.
linear data set (LDS)
A VSAM data set that contains data but no control information. A linear data set can be accessed as a byte-addressable string in virtual storage.
line response mode
A variation of response mode where all operations on the communication line are suspended while the application program output message is being generated. See also response mode and terminal response mode.
link
In an IMS multisystem environment, the connection between two systems. See also physical link and logical link.
linkage editor
A computer program for creating load modules from one or more object modules or load modules by resolving cross references among the modules and, if necessary, adjusting addresses.
link-edit
The action of creating a loadable computer program using a linkage editor.
list
A type of object, which DB2 utilities can process, that identifies multiple table spaces, multiple index spaces, or both. A list is defined with the LISTDEF utility control statement.
list entry
An entry on an coupling facility list structure list.
list entry controls
Part of a coupling facility list structure list entry that contains control information associated with the list entry such as the entry key and entry ID.
list header
Start of changeAnchors the list to a coupling facility list structure and contains control information associated with the list. End of change
list header number
The number of the list header, which identifies the particular list. The list header number ranges from 0 to the maximum defined by the first connector to the coupling facility list structure. The list header number must be specified on IXL requests that access the list structure, to identify to which list the request is applicable.
list structure
For DB2 A coupling facility structure that lets data be shared and manipulated as elements of a queue.
For IMS A coupling facility structure that enables multisystem applications in a sysplex to share information organized as a set of lists or queues. A list structure consists of a set of lists and an optional lock table, which can be used for serializing resources in the list structure. Each list consists of a queue of list entries.
literal field
In MFS, a message field or device output field defined to contain specific data. See also default literal, explicit literal, and system literal.
L-lock
See logical lock.
Start of changeload balancingEnd of change
Start of changeAn optional Fast Path facility that enables an application program to be scheduled into more than one message or batch message region at the same time. See also transaction load balancing.End of change
Start of changeload balancing groupEnd of change
Start of changeA grouping of Fast Path input messages that are ready for balanced processing by one or more copies of a Fast Path program. There is one load balancing group for each unique Fast Path message-driven application program.End of change
load module
A program unit that is suitable for loading into main storage for execution. The output of a linkage editor.
LOB
See large object.
LOB locator
A mechanism that allows an application program to manipulate a large object value in the database system. A LOB locator is a fullword integer value that represents a single LOB value. An application program retrieves a LOB locator into a host variable and can then apply SQL operations to the associated LOB value using the locator.
LOB lock
A lock on a LOB value.
LOB table space
Start of changeA table space that contains all the data for a particular LOB column in the related base table.End of change
local
A way of referring to any object that the local DB2 subsystem maintains. A local table, for example, is a table that is maintained by the local DB2 subsystem. Contrast with remote.
local cache
A user-allocated and user-managed storage area on the local system.
local destination
In an IMS multisystem environment, a destination that resides in the local system. See also remote destination.
locale
The definition of a subset of a user's environment that combines a CCSID and characters that are defined for a specific language and country.
local lock
For DB2 A lock that provides intra-DB2 concurrency control, but not inter-DB2 concurrency control; that is, its scope is a single DB2.
For IMS An IRLM lock that interests the IRLM that grants it only.
local lock management
Lock management that controls access to database records used by application programs in the same online IMS system.
Start of changelocal logical unit (local LU)End of change
Start of changeAny logical unit (LU), other than the defined base LU, that is used for outbound processing. See also logical unit.End of change
local recovery
Resource recovery in which all resources and participants reside on the same system.
local subsystem
The unique relational DBMS to which the user or application program is directly connected (in the case of DB2, by one of the DB2 attachment facilities).
local system
In an IMS multisystem environment, a specific system in the multiple configuration. The local system is often used synonymously with front-end system, or the system where the inputting terminal exists. See also remote system.
local transaction (LTRAN)
In a multisystem environment, a transaction that is processed totally by the system in which it is defined. See also remote transaction.
local view
A description of the data that a particular business process requires. It includes a list of the data elements, a conceptual data structure that shows how the data elements are grouped according to the entities they describe, and the relationships among the groups of data elements.
location
The unique name of a database server. An application uses the location name to access a DB2 database server. A database alias can be used to override the location name when accessing a remote server.
location alias
Another name by which a database server identifies itself in the network. Applications can use this name to access a DB2 database server.
lock
A means of controlling concurrent events or access to data. DB2 locking is performed by the IRLM.
lock duration
The interval over which a DB2 lock is held.
lock escalation
The promotion of a lock from a row, page, or LOB lock to a table space lock because the number of page locks that are concurrently held on a given resource exceeds a preset limit.
locking
Start of changeThe process by which the integrity of data is ensured. Locking prevents concurrent users from accessing inconsistent data. See also claim, drain, and latch.End of change
lock management
The reservation of a segment by a program. Other programs are kept from using the segment until the program using it is done.
lock mode
A representation for the type of access that concurrently running programs can have to a resource that a DB2 lock is holding.
lock object
The resource that is controlled by a DB2 lock.
lock promotion
The process of changing the size or mode of a DB2 lock to a higher, more restrictive level.
lock sequence number (LSN)
A unique number, issued sequentially, given to a database resource to identify that it is in use (locked) by a requestor. A locked resource cannot be used until the current requestor has finished using it.
lock size
The amount of data that is controlled by a DB2 lock on table data; the value can be a row, a page, a LOB, a partition, a table, or a table space.
lock structure
A coupling facility data structure that is composed of a series of lock entries to support shared and exclusive locking for logical resources.
log
A collection of records that describe the events that occur during DB2 execution and that indicate their sequence. The information thus recorded is used for recovery in the event of a failure during DB2 execution.
log control interval definition
A suffix of the physical log record that tells how record segments are placed in the physical control interval.
logical association
In a data-sharing environment, the association IMS makes between a VSO DEDB area and a multi-area structure when an XES connection exists between IMS and the structure.
logical child
In a database, a pointer segment that establishes an access path between its physical parent and its logical parent. It is a physical child of its physical parent; it is a logical child of its logical parent.
logical claim
A claim on a logical partition of a nonpartitioning index.
logical database
A set of logical database record occurrences. It is composed of one or more physical databases; it represents hierarchic, structured relationships between data segments that can be different from the physical structure in which the segments were loaded. Contrast with physical database.
logical database record
In a database, a set of hierarchically related segments of one or more segment types. As viewed by the application program, the logical database record is always a hierarchic tree structure of segments. All of the segments that exist hierarchically dependent to a given root segment and that root segment.
logical data structure
In a database, a hierarchic structure of segments. Application programs written to use IMS deal only with logical data structures.
logical destination
See destination, local destination, and remote destination.
logical index partition
The set of all keys that reference the same data partition.
logical link
In a multisystem environment, the means by which a physical link is related to the transactions and terminals that can use that physical link.
logical link path
In a multisystem environment, the path between any two systems. One or more logical link paths must be defined for each logical link.
logical lock (L-lock)
The lock type that transactions use to control intra- and inter-DB2 data concurrency between transactions. Contrast with physical lock (P-lock).
logical logging
The process of moving log records into the log buffers. See also physical logging.
logically complete
A state in which the concurrent copy process is finished with the initialization of the target objects that are being copied. The target objects are available for update.
logical messages
Input or output messages that are in a queue associated with a logical rather than a physical terminal. The message queue can be moved, independent of an application, from device to device.
logical page list (LPL)
A list of pages that are in error and that cannot be referenced by applications until the pages are recovered. The page is in logical error because the actual media (coupling facility or disk) might not contain any errors. Usually a connection to the media has been lost.
logical page (LPAGE)
In MFS, a user-defined group of related message segment and field definitions.
logical paging
In MFS, the means by which output message segments are grouped for formatting. See also operator logical paging.
logical parent
In a database, it is the segment a logical child points to. It can also be a physical parent. Furthermore, it contains the common reference data. The pointer in the logical child to the logical parent can be symbolic or direct.
logical partition
A set of key or RID pairs in a nonpartitioning index that are associated with a particular partition.
logical recovery pending (LRECP)
The state in which the data and the index keys that reference the data are inconsistent.
logical relationship
In a database, a user-defined path between two independent segments.
logical terminal (LTERM)
A message destination logically associated with a physical terminal or user. An LTERM is represented by a CNT control block. See also remote logical terminal.
logical terminal pool
A user-defined group of logical terminals to be associated with non-VTAM switched communication lines through the /IAM command. Each logical terminal pool consists of one or more logical terminal subpools.
logical terminal subpool
A user-defined group of logical terminals within a logical terminal pool. Each usage of the /IAM command from a non-VTAM switched terminal causes one logical terminal subpool to be associated with one physical terminal.
logical twins
In a database, all occurrences of one type of logical child with a common logical parent occurrence. See also physical twins.
logical unit (LU)
Start of changeFor DB2 An access point through which an application program accesses the SNA network in order to communicate with another application program. See also LU name.End of change
Start of changeFor IMS An addressable resource such as an application program, a terminal, or a subsystem. A logical unit can also be a component of general-purpose terminal systems, such as operator terminals, printers, and auxiliary control units. For IMS, an LU is usually a terminal that logs on to IMS to do work.End of change
logical unit of work
For DB2 The processing that a program performs between synchronization points.
For IMS The processing a program performs from one sync point to the next.
logical unit of work identifier (LUWID)
A name that uniquely identifies a thread within a network. This name consists of a fully-qualified LU network name, an LUW instance number, and an LUW sequence number.
log initialization
The first phase of restart processing during which DB2 attempts to locate the current end of the log.
logon descriptor
An ETO descriptor that provides information required by IMS to build terminal-related control blocks.
log record header (LRH)
Start of changeA prefix, in every log record, that contains control information.End of change
log record identifier (LRID)
A sequence number used to identify a log record and to maintain the order of log records for a subsystem.
log record sequence number (LRSN)
An identifier for a log record that is associated with a data sharing member. DB2 uses the LRSN for recovery in the data sharing environment.
log router
In an RSR environment, the component of the tracking subsystem that receives log data from active subsystems, stores the data in tracked log data sets, and routes the log records to tracking components.
log sequence number (LSN)
Equivalent to the log record identifier (LRID). See log record identifier.
log token
Start of changeA token that identifies a particular log record in the z/OS log stream that is used to locate that log record.End of change
log truncation
A process by which an explicit starting RBA is established. This RBA is the point at which the next byte of log data is to be written.
log write-ahead (LWA)
The process of logging records of completed operations to the write-ahead data set before entering them in the online log data set.
looptest mode
The test mode that permits the establishment of an output write loop, whereby continuous attempts are made to transmit a user-entered message to the test terminal.
LPAGE
See logical page.
LPL
See logical page list.
LRECP
See logical recovery pending.
LRH
See log record header.
LRID
See log record identifier.
LRSN
See log record sequence number.
LSN
See log sequence number.
LTERM
See logical terminal.
LTRAN
See local transaction.
LU
See logical unit.
LU 6.2 destination
Start of changeAn LU 6.2 application program that is defined by an LU (logical unit) name, plus a transaction program name. End of change
LU name
Logical unit name, which is the name by which VTAM refers to a node in a network.
LUW
See logical unit of work.
LUWID
Start of changeSee logical unit of work identifier. End of change
MADS
Start of changeSee multiple area data set.End of change
main storage database (MSDB)
A root-segment database that resides in virtual storage. The data in an MSDB is stored in segments. Each segment can be available to all terminals or assigned to a specific terminal; however, segments cannot be assigned to a terminal that is defined through ETO.
mapping table
A table that the REORG utility uses to map the associations of the RIDs of data records in the original copy and in the shadow copy. This table is created by the user.
marooned log data
In an RSR environment, the active IMS log data, at the remote site, that follows a gap in the log data. Marooned log data cannot be processed by the tracking IMS until the log data that fills the gap has been received.
mass delete
The deletion of all rows of a table.
master
The client that initiates a process step.
master CQS
The CQS that coordinates a sysplex-wide task. The other CQSs sharing in the task are participants. If the master CQS fails for any reason, another CQS takes over the role of master and either continues or aborts the task.
master database
In an RSR environment, a database at the active site. If a remote takeover occurs, the shadow database becomes the master database.
master terminal
The IMS logical terminal that has complete control of IMS resources during online operations.
master terminal formatting option
An MFS option that provides a format for a 3270 master terminal.
materialize
  • The process of putting rows from a view or nested table expression into a work file for additional processing by a query.
  • The placement of a LOB value into contiguous storage. Because LOB values can be very large, DB2 avoids materializing LOB data until doing so becomes absolutely necessary.
materialized query table
Start of changeA table that is used to contain information that is derived and can be summarized from one or more source tables. Contrast with base table.End of change
MB
Megabyte (1 048 576 bytes).
MBCS
Start of changeSee multibyte character set. End of change
member
See group member, IMSplex member, generic resource member.
member name
The z/OS XCF identifier for a particular DB2 subsystem in a data sharing group.
menu
A displayed list of available functions for selection by the operator. A menu is sometimes called a menu panel.
message
Data transmitted between any two terminals, application programs, and IMS systems. Each message has one or more segments.
message class
A class, assigned to a transaction code, that determines within which message region an application program is to process that transaction. See also region class and transaction code.
Message Control Information
The part of the OTMA message prefix that contains such information as the transaction pipe name and the message type. It is not contiguous with the rest of the message prefix and it must be specified for every OTMA message.
message delete option
An option that may be defined to prevent nonessential messages from being sent to a specific terminal.
message destination
A destination that is a transaction, an LTERM, an MSNAME, or a command.
message-driven program
An application program that is initiated by the scheduling of an input message. The types of message-driven programs are MPP, IFP, and JMP. See also non-message-driven program.
message editing
The process by which messages are formatted for presentation to an application program or terminal. Additional message editing routines may be written by the user. See also basic edit and Message Format Service.
message field (MFLD)
In MFS, the smallest area in a message input or output descriptor whose content and structure are defined by the user.
Start of changemessage flood conditionEnd of change
Start of changeWhen the number of incoming messages that are waiting to be processed by OTMA threatens IMS performance or rises above acceptable limits. A message flood condition occurs when too many transactions are waiting to be processed by OTMA, and can deplete all available local system queue area (LSQA) storage and result in a z/OS abend.End of change
Message Format Service (MFS)
An editing facility that allows application programs to deal with simple logical messages instead of device-dependent data, thus simplifying the application development process.
Message Format Service (MFS) control block
In MFS, the representation of a message or format that is stored in the IMS.FORMAT library and called into the MFS buffer pool as needed for online execution. See also message input descriptor, message output descriptor, device input format, and device output format.
message input descriptor (MID)
The MFS control block that describes the format of the data presented to the application program.
message mode
A transaction attribute that describes how the transaction is handled by the application program. See also single-message mode and multiple message mode.
message output descriptor (MOD)
The MFS control block that describes the format of the output data produced by the application program.
message prefix
Each message in IMS contains a message prefix. This is a structured set of areas that define information needed for processing each message. Some parts of the message prefix always exist, while others are only included if the IMS system is defined with a particular function.
message processing program (MPP)
An IMS application program that is driven by transactions and has access to online IMS databases and message queues. See also batch message processing program and batch processing program.
message queue
The data structure in which messages are queued before being processed by an application program or sent to a terminal. Local message queues are in IMS control regions and shared message queues are in coupling facility structures. See also shared queue.
message recovery point
The last inbound message for which IMS returned a definite response or the last outbound message for which IMS requested a definite response.
message resynchronization
A facility that detects and corrects a lost message condition if a network failure occurs.
message segment
The unit of access when referring to a message to or from a terminal.
message switch
A terminal input message directed to another terminal without being processed by a message processing program. See also program-to-program message switch.
metalanguage
A language that is used to create other specialized languages.
MFLD
See message field.
MFS
See Message Format Service.
MFS device descriptor
A descriptor used by ETO to update screen size in the DCT and generate new MFS default formats without system generation.
MFS dynamic directory
Start of changeA technique that is used by the online IMS control program, when operating under z/OS, to manage message format control blocks that are stored in extended private storage.End of change
MFSTEST
An optional MFS facility that allows MFS control blocks to be created and tested online without disrupting production activity.
MID
See message input descriptor.
migration
The process of converting a subsystem with a previous release of DB2 to an updated or current release. In this process, you can acquire the functions of the updated or current release without losing the data that you created on the previous release.
mixed data string
A character string that can contain both single-byte and double-byte characters.
mixed-mode BMP
An IMS batch messaging program that has access to Fast Path and full-function databases.
MOD
See message output descriptor.
mode name
A VTAM name for the collection of physical and logical characteristics and attributes of a session.
modifiable alternate PCB
An alternate PCB for which the destination can be changed by the application program during execution.
modified standard DL/I application program
An application program that uses CPI-C calls to allocate additional LU 6.2 conversations to the same or different LU 6.2 devices, and sends and receives data.
modify locks
An L-lock or P-lock with a MODIFY attribute. A list of these active locks is kept at all times in the coupling facility lock structure. If the requesting DB2 subsystem fails, that DB2 subsystem's modify locks are converted to retained locks.
MPP
See message processing program.
MSC
See Multiple Systems Coupling.
MSC descriptor
A descriptor used by ETO to relate LTERMs to statically defined MSC links.
Start of changeMSC directed routingEnd of change
In an IMS multisystem environment, the routing of response messages to other than the originating terminal as directed by a link receive routing exit routine.
MSDB
See main storage database.
MSNAME
An IMS macro used to define a name that represents remote and local system identifiers (SYSIDs). This name is a destination name for IMS messages sent to remote IMS systems with MSC. The link name on the MSNAME macro, transaction names, and LTERM names must be unique. The MSNAME is represented by the LNB control block.
MTO
See master terminal.
multibyte character set (MBCS)
Start of changeA character set that represents single characters with more than a single byte. UTF-8 is an example of an MBCS. Characters in UTF-8 can range from 1 to 4 bytes in DB2. Contrast with single-byte character set and double-byte character set. See also Unicode. End of change
multidimensional analysis
The process of assessing and evaluating an enterprise on more than one level.
Start of changemultiple area data set (MADS)End of change
Multiple data sets that contain shadow copies of DEDB areas. See also area data sets.
multiple-area structure
In a data-sharing environment, a coupling facility structure that contains more than one VSO DEDB area. See also single-area structure.
multiple message mode
A processing mode in which synchronization points occur only at DL/I CHKP calls or application termination. See also single-message mode, synchronization point.
Multiple Systems Coupling (MSC)
An IMS facility that permits geographically dispersed IMSs to communicate with one another. See also IMSplex.
Multiple Virtual Storage (MVS)
An element of the z/OS operating system. This element is also called the Base Control Program (BCP).
multisite update
Distributed relational database processing in which data is updated in more than one location within a single unit of work.
multisystem environment
Two or more (up to 255) IMS systems that run on any supported systems in one or more CPCs; the environment in which Multiple System Coupling runs.
multithreading
Multiple TCBs that are executing one copy of DB2 ODBC code concurrently (sharing a processor) or in parallel (on separate central processors).
MVS
See Multiple Virtual Storage.
name type
Start of changeA 1-byte number from 1 to 255 that the client specifies as the first byte of the resource ID. The name type guarantees uniqueness of names for all resources of that name type. This uniqueness prevents clients from putting more than one resource with the same name and name type out on the resource structure. The resources within the name type can have different data resource types.End of change
Start of changenative SQL procedureEnd of change
Start of changeAn SQL procedure that is processed by converting the procedural statements to a native representation that is stored in the database directory, as is done with other SQL statements. When a native SQL procedure is called, the native representation is loaded from the directory, and DB2 executes the procedure. Contrast with external procedure and external SQL procedure. End of change
nested table expression
A fullselect in a FROM clause (surrounded by parentheses).
network identifier (NID)
The network ID that is assigned by IMS or CICS, or if the connection type is RRSAF, the RRS unit of recovery ID (URID).
Start of changenew-function mode (NFM)End of change
Start of changeThe normal mode of operation that exists after successful completion of a version-to-version migration. At this stage, all new functions of the new version are available for use. A DB2 data sharing group cannot coexist with members that are still at the prior version level, and fallback to a prior version is not supported. Contrast with compatibility mode, compatibility mode*, enabling-new-function mode, and enabling-new-function mode*.End of change
NFM
Start of changeSee new-function mode.End of change
NID
See network identifier.
node
Start of changeAn IMS resource that represents a physical VTAM terminal. The node is represented by a VTAM termincal control block (TCB).End of change
Start of changenode ID indexEnd of change
Start of changeSee XML node ID index. End of change
nondeterministic function
Start of changeA user-defined function whose result is not solely dependent on the values of the input arguments. That is, successive invocations with the same argument values can produce a different answer. This type of function is sometimes called a variant function. Contrast with deterministic function (sometimes called a not-variant function).End of change
non-ISC static user
A user signed on to a static terminal. The user is represented by a user ID that is defined to an enhanced security product such as RACF.
nonleaf page
Start of changeA page that contains keys and page numbers of other pages in the index (either leaf or nonleaf pages). Nonleaf pages never point to actual data. Contrast with leaf page. End of change
non-message-driven program
An application program that is initiated by the submission of a batch job. This program runs in either a BMP region, JBP region, or an IFP utility region. See also message-driven program.
nonpartitioned index
An index that is not physically partitioned. Both partitioning indexes and secondary indexes can be nonpartitioned.
nonpartitioned secondary index (NPSI)
An index on a partitioned table space that is not the partitioning index and is not partitioned. Contrast with data-partitioned secondary index.
nonpartitioning index
See secondary index.
nonrecoverable status
Any resource status that cannot be recovered after a terminal logoff, a user signoff, or an IMS restart. Nonrecoverable status only exists while the resource is active and is deleted when that resource becomes inactive.
nonrecoverable transaction
An inquiry transaction that is not recovered in the event of a failure.
nonscrollable cursor
A cursor that can be moved only in a forward direction. Nonscrollable cursors are sometimes called forward-only cursors or serial cursors.
non-terminal-related MSDB
A type of MSDB characterized by data that is used or updated frequently and segments that are not owned by specific logical terminals. Direct update of segment fields is allowed but no insertion or deletion of segments is permitted.
normalization
A key step in the task of building a logical relational database design. Normalization helps you avoid redundancies and inconsistencies in your data. An entity is normalized if it meets a set of constraints for a particular normal form (first normal form, second normal form, and so on). Contrast with denormalization.
normal priority
The priority assigned to a transaction when the number of transactions enqueued and waiting to be processed is less than the limit count value. See also limit count, limit priority.
normal restart
The restart of IMS after a termination initiated by a /CHECKPOINT command. See also emergency restart.
normal XRF operations
The period of XRF processing when the active IMS is processing the IMS workload and the alternate IMS is tracking the active IMS.
not-variant function
See deterministic function.
NPSI
See nonpartitioned secondary index.
NUL
The null character ('\0'), which is represented by the value X'00'. In C, this character denotes the end of a string.
null
A special value that indicates the absence of information.
null output message
The message IMS sends to a terminal when no other output is immediately available to satisfy terminal requirements.
null terminator
Start of changeIn C, the value that indicates the end of a string. For EBCDIC, ASCII, and Unicode UTF-8 strings, the null terminator is a single-byte value (X'00'). For Unicode UTF-16 or UCS-2 (wide) strings, the null terminator is a double-byte value (X'0000'). End of change
ODBA
See Open Database Access.
ODBC
See Open Database Connectivity.
ODBC driver
A dynamically-linked library (DLL) that implements ODBC function calls and interacts with a data source.
OFR
See online forward recovery.
Start of changeOLAPEnd of change
Start of changeSee online analytical processing.End of change
OLDS
See online log data set.
OLIC
See online image copy (OLIC).
OM
See Operations Manager.
OM API
The API that enables users to write single points of control that communicate with OM.
online
Applicable in the IMS DB/DC, DBCTL, and DCCTL environments, unless otherwise indicated.
Start of changeonline analytical processing (OLAP)End of change
Start of changeThe process of collecting data from one or many sources; transforming and analyzing the consolidated data quickly and interactively; and examining the results across different dimensions of the data by looking for patterns, trends, and exceptions within complex relationships of that data.End of change
online change
An IMS function that supports the adding, changing, or deleting of IMS resources online such as transactions, database directories, program directories, DMBs, PSBs, and Fast Path routing codes without stopping the system to define them.
online forward recovery
Start of changeIn an RSR environment, the process by which a stopped shadow database or area is brought to currency with the database or area on the active IMS by the tracking IMS.End of change
online image copy (OLIC)
Start of changeThe process of creating an image copy while the database is online. Also, the image copy that is created by the online image copy process.End of change
online log data set (OLDS)
A data set on direct access storage that contains the log records written by an online IMS system.
online reorganization
Database reorganization, which is available only for HALDBs and DEDBs, during which the database remains available for updates during the reorganization process.
Open Database Access (ODBA)
A callable interface that can be used by an z/OS application program to issue DL/I calls to an IMS DB system. The application program must use the RRS of z/OS as a sync-point manager.
Open Database Connectivity (ODBC)
A Microsoft database application programming interface (API) for C that allows access to database management systems by using callable SQL. ODBC does not require the use of an SQL preprocessor. In addition, ODBC provides an architecture that lets users add modules called database drivers, which link the application to their choice of database management systems at run time. This means that applications no longer need to be directly linked to the modules of all the database management systems that are supported.
Open Transaction Manager Access (OTMA)
A transaction-based, connectionless client/server protocol. Its implementation is specific to IMS in a sysplex environment. The domain of the protocol is restricted to the domain of the Cross-System Coupling Facility (XCF). OTMA is designed to be a high-performance comprehensive protocol that allows clients (z/OS applications) to submit transactions to IMS or issue IMS commands and receive output from IMS application programs and from IMS itself.
Operations Manager (OM)
In an IMSplex, a CSL component that receives commands from AOPs, routes the command to IMSplex members, consolidates commands responses, and sends the responses to the AOP.
operator control function
In MFS, the means by which a terminal operator controls the display of output messages. Specific operator control functions are provided by IMS, but their use must be defined by the user in an operator control table.
operator control table
In MFS, a user-defined table of operator control functions; when a table is used, a specific control function is invoked when the input device data or data length satisfies a predefined condition.
operator logical paging
An MFS facility that allows the device operator to request a specific logical page of an output message.
ordinary identifier
An uppercase letter followed by zero or more characters, each of which is an uppercase letter, a digit, or the underscore character. An ordinary identifier must not be a reserved word.
ordinary token
A numeric constant, an ordinary identifier, a host identifier, or a keyword.
originating task
In a parallel group, the primary agent that receives data from other execution units (referred to as parallel tasks) that are executing portions of the query in parallel.
OSAM
See Overflow Sequential Access Method.
OTMA
See Open Transaction Manager Access.
outer join
The result of a join operation that includes the matched rows of both tables that are being joined and preserves some or all of the unmatched rows of the tables that are being joined. See also join, equijoin, full outer join, inner join, left outer join, and right outer join.
output message
A valid response mode message, a conversational mode message, an exclusive mode message, an IMS system message, an application program message, or a message switch.
overflow area
In an HDAM or PHDAM database, the area in which IMS stores data when the root addressable area does not have enough space for a segment. Contrast with root addressable area.
Overflow Sequential Access Method (OSAM)
An IMS data management access method that combines selected characteristics of BSAM and BDAM. OSAM is used by the following IMS database access methods: HISAM, HIDAM, and HDAM if VSAM is not used. OSAM is also used by some of the online pool management routines.
overflow structure
A coupling facility list structure that contains shared queues when the primary structure reaches a user-specified overflow threshold. The overflow structure is optional. See also primary structure.
overloaded function
A function name for which multiple function instances exist.
package
An object containing a set of SQL statements that have been statically bound and that is available for processing. A package is sometimes also called an application package.
package list
An ordered list of package names that may be used to extend an application plan.
package name
Start of changeThe name of an object that is used for an application package or an SQL procedure package. An application package is a bound version of a database request module (DBRM) that is created by a BIND PACKAGE or REBIND PACKAGE command. An SQL procedural language package is created by a CREATE or ALTER PROCEDURE statement for a native SQL procedure. The name of a package consists of a location name, a collection ID, a package ID, and a version ID. End of change
page
Start of changeA unit of storage within a table space (4 KB, 8 KB, 16 KB, or 32 KB) or index space (4 KB, 8 KB, 16 KB, or 32 KB). In a table space, a page contains one or more rows of a table. In a LOB or XML table space, a LOB or XML value can span more than one page, but no more than one LOB or XML value is stored on a page.End of change
page set
Another way to refer to a table space or index space. Each page set consists of a collection of VSAM data sets.
page set recovery pending (PSRCP)
A restrictive state of an index space. In this case, the entire page set must be recovered. Recovery of a logical part is prohibited.
panel
A predefined display image that defines the locations and characteristics of display fields on a display surface (for example, a menu panel).
parallel complex
A cluster of machines that work together to handle multiple transactions and applications.
parallel DL/I
A facility that permits all database calls to be processed in each message processing region or batch message processing region.
parallel group
A set of consecutive operations that execute in parallel and that have the same number of parallel tasks.
parallel I/O processing
A form of I/O processing in which DB2 initiates multiple concurrent requests for a single user query and performs I/O processing concurrently (in parallel) on multiple data partitions.
parallelism assistant
In Sysplex query parallelism, a DB2 subsystem that helps to process parts of a parallel query that originates on another DB2 subsystem in the data sharing group.
parallelism coordinator
In Sysplex query parallelism, the DB2 subsystem from which the parallel query originates.
Parallel Sysplex
A set of z/OS systems that communicate and cooperate with each other through certain multisystem hardware components and software services to process customer workloads.
parallel task
The execution unit that is dynamically created to process a query in parallel. A parallel task is implemented by a z/OS service request block.
parameter marker
Start of changeA question mark (?) that appears in a statement string of a dynamic SQL statement. The question mark can appear where a variable could appear if the statement string were a static SQL statement. End of change
parameter-name
Start of changeAn SQL identifier that designates a parameter in a routine that is written by a user. Parameter names are required for SQL procedures and SQL functions, and they are used in the body of the routine to refer to the values of the parameters. Parameter names are optional for external routines.End of change
parent key
A primary key or unique key in the parent table of a referential constraint. The values of a parent key determine the valid values of the foreign key in the referential constraint.
parent lock
For explicit hierarchical locking, a lock that is held on a resource that might have child locks that are lower in the hierarchy. A parent lock is usually the table space lock or the partition intent lock. See also child lock.
parent row
A row whose primary key value is the foreign key value of a dependent row.
parent segment
In a database, a segment that has one or more dependent segments (its children) hierarchically below it.
parent table
A table whose primary key is referenced by the foreign key of a dependent table.
parent table space
A table space that contains a parent table. A table space containing a dependent of that table is a dependent table space.
participant
An entity other than the commit coordinator that takes part in the commit process. The term participant is synonymous with agent in SNA.
partition
Start of changeFor DB2 A portion of a page set. Each partition corresponds to a single, independently extendable data set. The maximum size of a partition depends on the number of partitions in the partitioned page set. All partitions of a given page set have the same maximum size.End of change
For IMS
  • A subset of a HALDB that has the capacity of a non-HALDB database and that can be administered independently.
  • Refers to that part of a display used as the viewport, its associated window, and its display data buffer when in partitioned state.
Start of changepartition-by-growth table spaceEnd of change
Start of changeA table space whose size can grow to accommodate data growth. DB2 for z/OS manages partition-by-growth table spaces by automatically adding new data sets when the database needs more space to satisfy an insert operation. Contrast with range-partitioned table space. See also universal table space.End of change
partition descriptor block (PDB)
A collection of partition descriptor entries representing a partition set. An intermediate text block (ITB) for the PDB is created by the MFS Language Utility. This PDB ITB is used in creating a part of the DOF.
partition descriptor (PD)
This represents an entry in the PDB for a partition in a partition set. The entry is created by the MFS Language Utility using the PD statement and is referenced by the DPAGE statement PD operand. It contains all of the information necessary to issue the "CREATE PARTITION" Write Structured Field Command for the partition.
partitioned data set (PDS)
Start of changeA data set in disk storage that is divided into partitions, which are called members. Each partition can contain a program, part of a program, or data. A program library is an example of a partitioned data set. End of change
partitioned HDAM (PHDAM)
A partitioned Hierarchical Direct Access Method database organization, one type of High Availability Large Database (HALDB).
partitioned HIDAM (PHIDAM)
A partitioned Hierarchical Indexed Direct Access Method database organization, one type of High Availability Large Database (HALDB).
partitioned index
An index that is physically partitioned. Both partitioning indexes and secondary indexes can be partitioned.
partitioned page set
A partitioned table space or an index space. Header pages, space map pages, data pages, and index pages reference data only within the scope of the partition.
partitioned secondary index (PSINDEX)
A partitioned secondary index database organization, one type of High Availability Large Database (HALDB).
partitioned table space
Start of changeA table space that is based on a single table and that is subdivided into partitions, each of which can be processed independently by utilities. Contrast with segmented table space and universal table space.End of change
partitioning index
An index in which the leftmost columns are the partitioning columns of the table. The index can be partitioned or nonpartitioned.
partition set
All of the partitions that are defined in the partition descriptor block (PDB).
partition specification table (PST)
An IMS control block that contains dependent-region information.
partner logical unit
An access point in the SNA network that is connected to the local DB2 subsystem by way of a VTAM conversation.
partner LU
A remote LU with which a local LU establishes a session or allocates a conversation.
partner systems
In an IMS multisystem environment, two IMS online systems that are connected by an MSC link.
password security
The use of system definition macros and Security Maintenance utility control statements to restrict the use of IMS resources (databases, application programs, physical and logical terminals, transactions, and commands) to a person or persons who can supply the correct password.
path
For DB2 See SQL path.
For IMS
  • In a database, a sequence of segment occurrences from the root to an individual segment.
  • In an online IMS system, the route a message takes from the time it is originated through processing; in a multisystem environment, the route can include more than one IMS system.
path call
A type of DL/I call that enables a hierarchical path of segments to be inserted or retrieved with one call.
PCB
See program communication block (PCB).
PCB mask
A data structure in an application program in which IMS puts the status of the application program's DL/I calls. See also status code.
PD
See partition descriptor.
PDB
See partition descriptor block.
PDS
See partitioned data set.
PHDAM
See partitioned HDAM.
PHIDAM
See partitioned HIDAM.
physical child
In a database, a segment type that is dependent on a segment type defined at the next higher level in the database hierarchy. All segment types in a database, except the root, are physical children since each is dependent on at least the root.
physical consistency
The state of a page that is not in a partially changed state.
physical database
An ordered set of physical database records. Contrast with logical database.
physical database record
In databases, a physical set of hierarchically related segments of one or more segment types.
physical database record occurrence
An instance of a root segment and the hierarchical arrangement of all its dependent segment occurrences.
physical data structure
A hierarchy representing segment types and the hierarchic arrangement of those segment types in a physical database.
physical link
In an MSC network, the actual hardware connection between two systems. See also logical link.
physical lock (P-lock)
A type of lock that DB2 acquires to provide consistency of data that is cached in different DB2 subsystems. Physical locks are used only in data sharing environments. Contrast with logical lock (L-lock).
physical logging
The process of writing log records from the log buffers to the system log. See also logical logging.
physically complete
The state in which the concurrent copy process is completed and the output data set has been created.
physical page
In MFS, all or part of a logical page that is defined to be entered (input) or displayed (output) at one time.
physical paging
An MFS facility that permits data from a logical page to be displayed in several physical pages on the device.
physical parent
In a database, a segment type that has a dependent segment type defined at the next lower level in the physical database hierarchy.
physical relationship
In a database, the description of the relationship that exists between two or more physical segments.
physical segment
In a database, the smallest unit of accessible data.
physical terminal (PTERM)
A hardware device attached to the computer and supported by the DC feature as a terminal. A physical terminal usually has one or more logical terminals associated with it.
physical twins
In a database, all occurrences of a single physical child segment type that have the same (single occurrence) physical parent segment type. See also twin segments and logical twins.
PI
See program isolation.
piece
A data set of a nonpartitioned page set.
plan
See application plan.
plan allocation
The process of allocating DB2 resources to a plan in preparation for execution.
plan member
The bound copy of a DBRM that is identified in the member clause.
plan name
The name of an application plan.
planned remote takeover
In an RSR environment, a remote takeover initiated by the IMS operator as part of shutting down the IMSs at the active site in order to transfer the active IMS workload to the remote site.
planned takeover
An XRF takeover that an operator initiates.
P-lock
See physical lock.
point of consistency
A time when all recoverable data that an application accesses is consistent with other data. The term point of consistency is synonymous with sync point or commit point.
policy
See CFRM policy.
postponed abort UR
A unit of recovery that was inflight or in-abort, was interrupted by system failure or cancellation, and did not complete backout during restart.
post-takeover
The XRF phase, immediately following takeover, when the new active IMS system does not have alternate.
precision
In SQL, the total number of digits in a decimal number (called the size in the C language). In the C language, the number of digits to the right of the decimal point (called the scale in SQL). The DB2 information uses the SQL terms.
precompilation
A processing of application programs containing SQL statements that takes place before compilation. SQL statements are replaced with statements that are recognized by the host language compiler. Output from this precompilation includes source code that can be submitted to the compiler and the database request module (DBRM) that is input to the bind process.
predicate
An element of a search condition that expresses or implies a comparison operation.
prefix
A code at the beginning of a message or record.
preformat
Start of changeThe process of preparing a VSAM linear data set for DB2 use, by writing specific data patterns. End of change
preload
To load the root addressable portion and independent overflow portion of a VSO DEDB area into a data space when the area is opened.
preopen
To open a DEDB area after the first checkpoint following IMS control region initialization or during /START AREA command processing. If an area is not preopened, it will be opened during the first read request for the area.
prepare
The first phase of a two-phase commit process in which all participants are requested to prepare for commit.
prepared SQL statement
A named object that is the executable form of an SQL statement that has been processed by the PREPARE statement.
presentation space
The display data buffer associated with a partition. The size of the presentation space is defined as equal to, or larger than, the size of the viewport. When the presentation space is equal to the viewport size, all the data in the presentation space is displayed. When the presentation space is larger than the viewport, the user must move the scrolling window within the presentation space to display the data within the viewport. See also viewport.
preset destination mode
An optional mode of terminal operation that allows the destination of terminal input to be fixed as a specific transaction code or logical terminal. It is activated by the /SET command and reset by the /RESET command, the /STOP command, ETO user signoff, static terminal logoff, and an IMS restart.
primary authorization ID
The authorization ID that is used to identify the application process to DB2.
primary data set group
In a database, the first or only data set group defined. The root segment type always resides in the primary data set group. See also secondary data set group.
primary group buffer pool
For a duplexed group buffer pool, the structure that is used to maintain the coherency of cached data. This structure is used for page registration and cross-invalidation. The z/OS equivalent is old structure. Compare with secondary group buffer pool.
primary index
An index that enforces the uniqueness of a primary key.
primary key
In a relational database, a unique, nonnull key that is part of the definition of a table. A table cannot be defined as a parent unless it has a unique key or primary key.
primary request
In an MSC network, a message entered into a terminal before it is processed. See also secondary request and response.
primary session
The session between a class–1 terminal and the active IMS.
primary structure
A coupling facility list structure that contains shared queues or shared resources. See also overflow structure.
principal
An entity that can communicate securely with another entity. In Kerberos, principals are represented as entries in the Kerberos registry database and include users, servers, computers, and others.
principal name
The name by which a principal is known to the DCE security services.
private buffer pool
An area of local storage, used for VSO DEDB data, that can provide lookaside capability for shared VSO areas.
privilege
The capability of performing a specific function, sometimes on a specific object. See also explicit privilege.
privilege set
Start of change
  • For the installation SYSADM ID, the set of all possible privileges.
  • For any other authorization ID, including the PUBLIC authorization ID, the set of all privileges that are recorded for that ID in the DB2 catalog.
End of change
process
In DB2, the unit to which DB2 allocates resources and locks. Sometimes called an application process, a process involves the execution of one or more programs. The execution of an SQL statement is always associated with some process. The means of initiating and terminating a process are dependent on the environment.
processing intent
An application program attribute, defined in the PSB, that specifies the program's database access privileges such as, insert, delete, and replace.
processing limit
A transaction attribute that defines how many messages the application program is allowed to process during one program execution.
program
A single, compilable collection of executable statements in a programming language.
program communication block (PCB)
An IMS control block that describes an application program's interface to and view of an IMS database or, additionally for message processing and batch message processing programs, to the source and destinations of messages. PCBs are defined by the user during PSB generation. See also database program communication block (DB PCB) and telecommunication-program PCB.
program isolation (PI)
An IMS facility that separates all the activity of an application program from any other active application program until that application program indicates, using a synchronization point, that the data it has modified or created is consistent and complete.
program isolation (PI) lock manager
The facility that was formerly known as PI enqueue-dequeue. The PI lock manager is used for local locking in systems for which no IRLM has been defined. Otherwise, the IRLM is used for all lock management, including local.
program specification block generation (PSBGEN)
The process by which a PSB is created.
program specification block (PSB)
The control block that describes databases and logical message destinations used by an application program. A PSB consists of one or more PCBs. See also program communication block (PCB).
program temporary fix (PTF)
A solution or bypass of a problem that is diagnosed as a result of a defect in a current unaltered release of a licensed program. An authorized program analysis report (APAR) fix is corrective service for an existing problem. A PTF is preventive service for problems that might be encountered by other users of the product. A PTF is temporary, because a permanent fix is usually not incorporated into the product until its next release.
program-to-program message switch
An IMS output message sent by one application program to another application program.
prompt facility
An optional facility for notifying a terminal operator that a current page of output is the last page of a message.
protected conversation
For DB2 A VTAM conversation that supports two-phase commit flows.
For IMS A communication session that is allocated between two programs processing a transaction, that uses the sync point option, and that uses the two-phase commit and resynchronization protocols.
protected resource
A local or distributed resource for which updates are synchronized and controlled.
PSB
See program specification block.
PSBGEN
See program specification block generation.
pseudo-front-end system
An IMS in a multisystem environment in which all terminals are handled and a small number of time-consuming transactions are routed to a transaction processing system. See also, front-end system, and transaction processing system.
PSINDEX
See partitioned secondary index.
PSRCP
See page set recovery pending.
PST
See partition specification table.
PTERM
See physical terminal.
PTF
See program temporary fix.
Qbuffer
See queue buffer.
QMGR
See Queue Manager.
Qname
Queue Name. The name of a queue on Shared Queues upon which data objects reside. The queue name is 16 bytes long, left justified, padded with blanks. The first byte of the client queue name is the queue type. A client queue name of blanks or zeroes is supported.
QSAM
See queued sequential access method.
qualified call
A DL/I call that contains at least one segment search argument.
qualified segment search argument (SSA)
An SSA that contains, in addition to the segment name, one or more qualification statements. A qualified SSA describes the segment type and occurrence that is to be accessed.
query
A component of certain SQL statements that specifies a result table.
query block
Start of changeThe part of a query that is represented by one of the FROM clauses. Each FROM clause can have multiple query blocks, depending on DB2 processing of the query.End of change
query CP parallelism
Parallel execution of a single query, which is accomplished by using multiple tasks. See also Sysplex query parallelism.
query I/O parallelism
Parallel access of data, which is accomplished by triggering multiple I/O requests within a single query.
Start of changequeueEnd of change
A constructed and maintained list of items that are waiting to be processed. For example, a collection of data objects with the same name in a shared queue. Sometimes used synonymously with LTERM.
Start of changequeue bufferEnd of change
Start of changeAn IMS queue manager incore buffer that is used to keep the working copy of an IMS message segment.End of change
queued sequential access method (QSAM)
An extended version of the basic sequential access method (BSAM). When this method is used, a queue of data blocks is formed. Input data blocks await processing, and output data blocks await transfer to auxiliary storage or to an output device.
Queue Manager (QMGR)
An IMS component that manages IMS messages and the space the messages occupy. The IMS Queue Manager is part of a DB/DC or DCCTL environment.
queue structure
A structure managed by CQS that contains data in queues.
queue type
A grouping of shared queues on the coupling facility list structure whose meaning is client defined or CQS defined.
quiesce point
A point at which data is consistent as a result of running the DB2 QUIESCE utility.
RACF
Resource Access Control Facility. A component of the z/OS Security Server.
random read
Start of changeThe normal OSAM buffering method, which reads only one block with each I/O operation.End of change
Start of changerange-partitioned table spaceEnd of change
Start of changeA type of universal table space that is based on partitioning ranges and that contains a single table. Contrast with partition-by-growth table space. See also universal table space. End of change
Start of changeRapid Network Reconnect (RNR)End of change
A function of IMS that automatically reconnects IMS VTAM terminal sessions across outages (IMS, z/OS, or VTAM) and subsequent IMS restarts on the same or different z/OSs within a sysplex.
RAS
See resource access security (RAS).
RBA
See relative byte address.
RCT
See resource control table.
Start of changeRDDSEnd of change
Start of changeSee resource definition data set.End of change
Start of changeRDOEnd of change
Start of changeSee resource definition online. End of change
RDS
See restart data set.
read access
An access intent that establishes the intent of an application to read the database (without making modifications) and to be protected from an updater's incomplete changes. It allows other applications to share the database. It can also be called read with integrity.
readiness level
Start of changeFor an RSR database-level tracker, the level that determines whether a shadow database is ready to apply database changes as they are received from the active IMS. End of change
read-only access
Start of changeAn access intent that establishes the intent of an application to read the database without being protected from an updater's incomplete changes. Also called read without integrity.End of change
read stability (RS)
An isolation level that is similar to repeatable read but does not completely isolate an application process from all other concurrently executing application processes. See also cursor stabilityrepeatable read, and uncommitted read.
read with integrity
See read access.
read without integrity
See read-only access.
rebind
The creation of a new application plan for an application program that has been bound previously. If, for example, you have added an index for a table that your application accesses, you must rebind the application in order to take advantage of that index.
rebuild
The process of reallocating a coupling facility structure. For the shared communications area (SCA) and lock structure, the structure is repopulated; for the group buffer pool, changed pages are usually cast out to disk, and the new structure is populated only with changed pages that were not successfully cast out.
RECON
See recovery control (RECON) data set.
record
The storage representation of a row or other data.
record identifier (RID)
Start of changeA unique identifier that DB2 uses to identify a row of data in a table. Compare with row identifier.End of change
record identifier (RID) pool
An area of main storage that is used for sorting record identifiers during list-prefetch processing.
record length
The sum of the length of all the columns in a table, which is the length of the data as it is physically stored in the database. Records can be fixed length or varying length, depending on how the columns are defined. If all columns are fixed-length columns, the record is a fixed-length record. If one or more columns are varying-length columns, the record is a varying-length record.
record mode
In MFS, the default input mode in which fields are defined as occurring within a specific record sent from the device. See also stream mode.
recoverable resource
See protected resource.
Recoverable Resource Manager Services attachment facility (RRSAF)
A DB2 subcomponent that uses Resource Recovery Services to coordinate resource commitment between DB2 and all other resource managers that also use RRS in a z/OS system.
recoverable service element (RSE)
Start of changeAn IMS service element that is backed up and that can initiate a takeover.End of change
recoverable status
Any resource status that can be recovered after a terminal logoff, a user signoff, or an IMS restart.
recoverable transaction
An IMS transaction that is recovered in the event of a failure.
recovery
The process of rebuilding databases after a system failure.
recovery control (RECON) data set
Data sets in which DBRC stores information about logging activity and events that might affect the recovery of databases.
Start of changerecovery-level trackingEnd of change
Start of changeIn an RSR environment, a tracking IMS that does not track the databases or areas of the active IMSs, but instead saves all database changes on tracked logs on the tracking IMS until recovery or remote takeover is performed. See also database-level tracking.End of change
recovery log
A collection of records that describes the events that occur during DB2 execution and indicates their sequence. The recorded information is used for recovery in the event of a failure during DB2 execution.
recovery log data set (RLDS)
A log data set that contains only the log records that are required for database recovery.
recovery manager
A subcomponent that supplies coordination services that control the interaction of DB2 resource managers during commit, abort, checkpoint, and restart processes. The recovery manager also supports the recovery mechanisms of other subsystems (for example, IMS) by acting as a participant in the other subsystem's process for protecting data that has reached a point of consistency.
A coordinator or a participant (or both), in the execution of a two-phase commit, that can access a recovery log that maintains the state of the logical unit of work and names the immediate upstream coordinator and downstream participants.
recovery pending (RECP)
A condition that prevents SQL access to a table space that needs to be recovered.
recovery token
An identifier for an element that is used in recovery (for example, NID or URID).
RECP
See recovery pending.
redo
A state of a unit of recovery that indicates that changes are to be reapplied to the disk media to ensure data integrity.
reentrant code
Executable code that can reside in storage as one shared copy for all threads. Reentrant code is not self-modifying and provides separate storage areas for each thread. See also threadsafe.
referential constraint
The requirement that nonnull values of a designated foreign key are valid only if they equal values of the primary key of a designated table.
Start of changereferential cycleEnd of change
Start of changeA set of referential constraints such that each base table in the set is a descendent of itself. The tables that are involved in a referential cycle are ordered so that each table is a descendent of the one before it, and the first table is a descendent of the last table. End of change
referential integrity
The state of a database in which all values of all foreign keys are valid. Maintaining referential integrity requires the enforcement of referential constraints on all operations that change the data in a table on which the referential constraints are defined.
referential structure
A set of tables and relationships that includes at least one table and, for every table in the set, all the relationships in which that table participates and all the tables to which it is related.
refresh age
The time duration between the current time and the time during which a materialized query table was last refreshed.
region class
The class IMS assigns to a message region that indicates the message classes that can be processed within the region. See also message class.
registry
See registry database.
registry database
A database of security information about principals, groups, organizations, accounts, and security policies.
relational database
A database that can be perceived as a set of tables and manipulated in accordance with the relational model of data.
relational database management system (RDBMS)
A collection of hardware and software that organizes and provides access to a relational database.
Start of changerelational schemaEnd of change
Start of changeSee SQL schema. End of change
relationship
A defined connection between the rows of a table or the rows of two tables. A relationship is the internal representation of a referential constraint.
relative byte address (RBA)
The offset of a data record or control interval from the beginning of the storage space that is allocated to the data set or file to which it belongs.
remigration
The process of returning to a current release of DB2 following a fallback to a previous release. This procedure constitutes another migration process.
remote
Any object that is maintained by a remote DB2 subsystem (that is, by a DB2 subsystem other than the local one). A remote view, for example, is a view that is maintained by a remote DB2 subsystem. Contrast with local.
remote destination
In an MSC network, a destination that resides in a remote system. See also local destination.
remote logical terminal
An IMS queue associated with an MSC logical link to allow routing of asynchronous output messages to the local LTERM in another IMS.
remote site
In an RSR environment, the physically remote location of the tracking IMS and shadows databases. If a remote takeover occurs, it becomes the active site.
Remote Site Recovery (RSR)
A feature of IMS that minimizes the impact of active site failures by having a geographically remote IMS track active IMSs. Production work is taken over at the remote site in the event of a disaster or site-wide failure at the active site. See also tracking IMS.
remote subsystem
Any relational DBMS, except the local subsystem, with which the user or application can communicate. The subsystem need not be remote in any physical sense, and might even operate on the same processor under the same z/OS system.
remote system
In an MSC network, any IMS other than the local IMS.
remote takeover
In an RSR environment, an action initiated by an IMS operator to transfer the active IMS workload from the active site to the remote site. See also planned remote takeover, unplanned remote takeover.
remote terminal
A terminal that is not attached to the host system through an I/O channel.
remote transaction
In a multisystem environment, a transaction whose total processing is shared between two or more systems. See also local transaction.
reoptimization
The DB2 process of reconsidering the access path of an SQL statement at run time; during reoptimization, DB2 uses the values of host variables, parameter markers, or special registers.
Start of changereordered row formatEnd of change
Start of changeA row format that facilitates improved performance in retrieval of rows that have varying-length columns. DB2 rearranges the column order, as defined in the CREATE TABLE statement, so that the fixed-length columns are stored at the beginning of the row and the varying-length columns are stored at the end of the row. Contrast with basic row format.End of change
REORG pending (REORP)
A condition that restricts SQL access and most utility access to an object that must be reorganized.
REORP
See REORG pending.
repeatable read (RR)
The isolation level that provides maximum protection from other executing application programs. When an application program executes with repeatable read protection, rows that the program references cannot be changed by other programs until the program reaches a commit point. See also cursor stability, read stability, and uncommitted read.
repeating group
A situation in which an entity includes multiple attributes that are inherently the same. The presence of a repeating group violates the requirement of first normal form. In an entity that satisfies the requirement of first normal form, each attribute is independent and unique in its meaning and its name. See also normalization.
replay detection mechanism
A method that allows a principal to detect whether a request is a valid request from a source that can be trusted or whether an untrustworthy entity has captured information from a previous exchange and is replaying the information exchange to gain access to the principal.
reply
Synonymous with response in a non-VTAM environment.
request commit
The vote that is submitted to the prepare phase if the participant has modified data and is prepared to commit or roll back.
requester
The source of a request to access data at a remote server. In the DB2 environment, the requester function is provided by the distributed data facility.
resource
The object of a lock or claim, which could be a table space, an index space, a data partition, an index partition, or a logical partition.
resource access security (RAS)
The use of RACF security classes to protect resources (PSBs, transactions, and output LTERMs) from unauthorized use by a dependent region.
resource allocation
The part of plan allocation that deals specifically with the database resources.
resource class
A category of similar resources that are defined in the RACF class descriptor table (CDT).
resource control table
Start of changeA construct of previous versions of the CICS attachment facility that defines authorization and access attributes for transactions or transaction groups. Beginning in CICS Transaction Server Version 1.3, resources are defined by using resource definition online instead of the resource control table. See also resource definition online.End of change
Start of changeresource definition data set (RDDS)End of change
Start of changeA data set that manages IMS resources. IMS systems have options to export resources that are defined by the system definition process and resources that have been created or updated dynamically, into the RDDS. These resources can then be imported from the RDDS into an IMS system during cold start processing or through the use of an IMPORT command.End of change
Start of changeresource definition memberEnd of change
Start of changeA member in the IMS.PROCLIB data set that defines the resource definition data set (RDDS) to IMS. See also resource definition data set.End of change
resource definition online (RDO)
Start of changeThe recommended method of defining resources to CICS by creating resource definitions interactively, or by using a utility, and then storing them in the CICS definition data set. In earlier releases of CICS, resources were defined by using the resource control table (RCT), which is no longer supported.End of change
Start of changeresource descriptorEnd of change
Start of changeTemplates in which you define the attributes for a resource. You can then create a resource by using the resource descriptor to define the attributes for the resource.End of change
resource ID
Start of changeThe programmable list entry ID that IMS specifies for a resource to ensure name uniqueness. The first byte is the name type, and the remaining 11 bytes are the resource name, padded with blanks.End of change
resource limit facility (RLF)
A portion of DB2 code that prevents dynamic manipulative SQL statements from exceeding specified time limits. The resource limit facility is sometimes called the governor.
resource limit specification table (RLST)
A site-defined table that specifies the limits to be enforced by the resource limit facility.
resource manager
  • A function that is responsible for managing a particular resource and that guarantees the consistency of all updates made to recoverable resources within a logical unit of work. The resource that is being managed can be physical (for example, disk or main storage) or logical (for example, a particular type of system service).
  • A participant, in the execution of a two-phase commit, that has recoverable resources that could have been modified. The resource manager has access to a recovery log so that it can commit or roll back the effects of the logical unit of work to the recoverable resources.
Resource Manager (RM)
A CSL component that manages resources and coordinates online change for IMSs in an IMSplex.
resource name
Start of changeAn 11-byte unique name of a client-defined resource. A transaction is an example of an IMS resource name.End of change
resource structure
A coupling facility list structure, used by the Common Service Layer's Resource Manager and managed by CQS, that contains uniquely named resources. This structure is typically used to maintain global resource information when multiple Resource Managers exist in an IMSplex.
resource type
Start of changeA resource that is defined by CQS. CQS groups list headers into resource types. The resource types allow CQS and its clients to physically group resources of a particular type on a coupling facility list structure.End of change
response
A message inserted to a logical terminal destination specified by an I/O PCB or an alternate response PCB. When VTAM is used, the term reply is substituted for response because response has a separate meaning in VTAM communications. See also primary request, secondary request, and reply.
response alternate PCB
Synonym for alternate response PCB.
response mode
A mode of terminal operation that synchronizes operations between the terminal operator and the application program. When IMS receives an input transaction that causes response mode to be entered, no more input is allowed until the application program response has been transmitted back to the terminal. Response mode is activated when a transaction is entered at a terminal, if either the transaction or the terminal is defined as response mode. Reset by the /STOP command, ETO user signoff, static terminal logoff, and an IMS restart. See also line response mode and terminal response mode.
restart
See emergency restart and normal restart.
restart data set (RDS)
The direct-access data set that contains the information necessary to restart IMS.
restart pending (RESTP)
A restrictive state of a page set or partition that indicates that restart (backout) work needs to be performed on the object.
RESTP
See restart pending.
result set
The set of rows that a stored procedure returns to a client application.
result set locator
A 4-byte value that DB2 uses to uniquely identify a query result set that a stored procedure returns.
result table
The set of rows that are specified by a SELECT statement.
retained lock
Start of changeA MODIFY lock that a DB2 subsystem was holding at the time of a subsystem failure. The lock is retained in the coupling facility lock structure across a DB2 for z/OS failure.End of change
REXX SPOC API
An API that enables users to write REXX programs that communicate with OM.
RID
See record identifier.
RID pool
See record identifier pool.
right outer join
The result of a join operation that includes the matched rows of both tables that are being joined and preserves the unmatched rows of the second join operand. See also join, equijoin, full outer join, inner join, left outer join, and outer join.
RLDS
See recovery log data set.
RLF
See resource limit facility.
RLST
See resource limit specification table.
RLT
See recovery-level tracker.
RM
See Resource Manager.
RM affinity
Start of changeWhen RM and a resource structure are used, an association between an IMS and a user or node with LOCAL status recovery mode. If RM indicates that the user or node has RM affinity to an IMS, the user or node cannot log or sign on to another IMS. This affinity occurs because end-user significant status (conversation, set-and-test-sequence-numbers terminal, or Fast Path) is being recovered on an IMS.End of change
RNR
See Rapid Network Reconnect.
Start of changeroleEnd of change
Start of changeA database entity that groups together one or more privileges and that can be assigned to a primary authorization ID or to PUBLIC. The role is available only in a trusted context. End of change
rollback
The process of restoring data that was changed by SQL statements to the state at its last commit point. All locks are freed. Contrast with commit.
root addressable area
In an HDAM or PHDAM database, the primary storage area in HDAM and PHDAM databases. IMS always attempts to put new and updated segments in the root addressable area, and if there is not enough room, IMS puts the segment into the overflow area instead. Contrast with overflow area.
root anchor point (RAP)
In an HDAM database or DEDB, a pointer at the beginning of each block or CI that points to a root segment that belongs in that block and that chains the root segments that randomize to that CI or block.
root page
The index page that is at the highest level (or the beginning point) in an index.
root segment
The highest segment in the database hierarchy. The database is normally sequenced on the key of this segment. All other segments depend upon the root segment and reference it as part of their complete identity. See also dependent segment.
routine
Start of changeA database object that encapsulates procedural logic and SQL statements, is stored on the database server, and can be invoked from an SQL statement or by using the CALL statement. The main classes of routines are procedures and functions. End of change
routing code
For EMH, a user-defined code that allows transactions to be routed to programs within a load balancing group.
routing path
In an MSC network, the route through which IMS passes a message from its origination through processing. One or more systems may be included in a routing path.
row
The horizontal component of a table. A row consists of a sequence of values, one for each column of the table.
row identifier (ROWID)
A value that uniquely identifies a row. This value is stored with the row and never changes.
row lock
A lock on a single row of data.
row-positioned fetch orientation
Start of changeThe specification of the desired placement of the cursor as part of a FETCH statement, with respect to a single row (for example, NEXT, LAST, or ABSOLUTE n). Contrast with rowset-positioned fetch orientation.End of change
rowset
A set of rows for which a cursor position is established.
rowset cursor
A cursor that is defined so that one or more rows can be returned as a rowset for a single FETCH statement, and the cursor is positioned on the set of rows that is fetched.
rowset-positioned fetch orientation
Start of changeThe specification of the desired placement of the cursor as part of a FETCH statement, with respect to a rowset (for example, NEXT ROWSET, LAST ROWSET, or ROWSET STARTING AT ABSOLUTE n). Contrast with row-positioned fetch orientation.End of change
row trigger
A trigger that is defined with the trigger granularity FOR EACH ROW.
RRSAF
See Recoverable Resource Manager Services attachment facility.
RS
See read stability.
RSR
See Remote Site Recovery.
Start of changeruntime descriptor definitionEnd of change
Start of changeThe runtime template (in an internal format of control blocks) that can be used as a model when creating runtime resource definitions. See also runtime resource definition.End of change
Start of changeruntime resource definitionEnd of change
Start of changeThe resource information such as attributes, status, and relationships to other resources that IMS maintains at run time in an internal format called control blocks. The runtime resource definitions include, but are not limited to, database directories (DDIRs), program directories (PDIRs), data management blocks (DMBs), program specification blocks (PSBs), Fast Path routing codes (RCTEs), and scheduler message blocks (SMBs) or transactions.End of change
savepoint
A named entity that represents the state of data and schemas at a particular point in time within a unit of work.
SB
See sequential buffering.
SBCS
Start of changeSee single-byte character set. End of change
SCA
Start of changeFor DB2 See shared communications area. End of change
For IMS See system control area.
scalar function
Start of changeAn SQL operation that produces a single value from another value and is expressed as a function name, followed by a list of arguments that are enclosed in parentheses. End of change
scale
In SQL, the number of digits to the right of the decimal point (called the precision in the C language). The DB2 information uses the SQL definition.
SCD
See system contents directory.
Scheduler Message Block (SMB)
An IMS control block that represents a transaction.
scheduling intent
Start of changeAn application program attribute that is defined in the PSB, and that specifies how the program should be scheduled if multiple programs are contending for scheduling. See also exclusive access, read-only access, read access, and update access.End of change
scheduling priority
A transaction attribute that is used in calculating which transaction is selected for scheduling. See also normal priority and limit priority.
schema
The organization or structure of a database.
A collection of, and a way of qualifying, database objects such as tables, views, routines, indexes or triggers that define a database. A database schema provides a logical classification of database objects.
SCI
See Structured Call Interface.
scratchpad area (SPA)
A work area used in conversational processing to retain information from an application program across executions of the program.
scrollability
The ability to use a cursor to fetch in either a forward or backward direction. The FETCH statement supports multiple fetch orientations to indicate the new position of the cursor. See also fetch orientation.
scrollable cursor
A cursor that can be moved in both a forward and a backward direction.
scrolling window
The portion of the presentation space that is mapped to the viewport at any given time. The window can be moved vertically within the presentation space by scrolling. See also presentation space.
SCS
See SNA character string.
SDEP
See sequential dependent segment.
search condition
A criterion for selecting rows from a table. A search condition consists of one or more predicates.
search field
In a DL/I call, a field that is referred to by one or more SSAs.
secondary authorization ID
An authorization ID that has been associated with a primary authorization ID by an authorization exit routine.
secondary data set group
In a database, the data set group or groups defined in addition to the primary data set. A secondary data set group is normally defined to improve utilization of auxiliary storage. See also primary data set group.
secondary group buffer pool
For a duplexed group buffer pool, the structure that is used to back up changed pages that are written to the primary group buffer pool. No page registration or cross-invalidation occurs using the secondary group buffer pool. The z/OS equivalent is new structure.
secondary index
A nonpartitioning index that is useful for enforcing a uniqueness constraint, for clustering data, or for providing access paths to data for queries. A secondary index can be partitioned or nonpartitioned. See also data-partitioned secondary index (DPSI) and nonpartitioned secondary index (NPSI).
secondary index database
Start of changeAn index that is used to establish accessibility to a physical or logical database by a path that is different from the one provided by the database definition. A secondary index contains an index pointer segment type that is defined in a secondary index database.End of change
secondary logical unit (SLU)
A nonhost port through which the end user gains access to the services of the network. Normally, a nonhost program that resides within a controller or control unit.
secondary processing sequence
In a database, the hierarchic order of segment types in a physical or logical database that results automatically when a database is accessed through a secondary index.
secondary request
In a multisystem environment, a message inserted to a transaction code destination by an application program. See also primary request and response.
section
The segment of a plan or package that contains the executable structures for a single SQL statement. For most SQL statements, one section in the plan exists for each SQL statement in the source program. However, for cursor-related statements, the DECLARE, OPEN, FETCH, and CLOSE statements reference the same section because they each refer to the SELECT statement that is named in the DECLARE CURSOR statement. SQL statements such as COMMIT, ROLLBACK, and some SET statements do not use a section.
security
See password security, resource access security, signon verification, terminal security, and transaction command security.
Start of changesecurity labelEnd of change
Start of changeA classification of users' access to objects or data rows in a multilevel security environment." End of change
segment
For DB2 A group of pages that holds rows of a single table. See also segmented table space.
For IMS The unit of access; for the DB system, the smallest amount of data that can be transferred by one IMS operation. For input terminal operations using IMS TM, a segment is defined by the particular terminal type and is obtained by an application program with one call. See also segment occurrence and message segment.
segmented table space
Start of changeA table space that is divided into equal-sized groups of pages called segments. Segments are assigned to tables so that rows of different tables are never stored in the same segment. Contrast with partitioned table space and universal table space.End of change
segment occurrence
In a database, an instance of a segment type.
segment search argument (SSA)
The portion of a DL/I call that identifies a segment or group of segments to be processed. Each SSA contains a segment name and, optionally, one or more command codes, and one or more qualification statements. Multiple SSAs may be required to identify the desired segment. See also qualified segment search argument and unqualified SSA.
segment type
In a database, a user-defined category of data. See also segment occurrence.
selection priority
See scheduling priority.
self-referencing constraint
A referential constraint that defines a relationship in which a table is a dependent of itself.
self-referencing table
A table with a self-referencing constraint.
sensitive cursor
A cursor that is sensitive to changes that are made to the database after the result table has been materialized.
sensitive segment
A segment type in a database to which an application program is sensitive.
sensitivity (program)
An IMS capability that ensures that only data segments or fields predefined as "sensitive" are available for use in a particular application. The sensitivity concept also provides a degree of control over data security, inasmuch as users can be prevented from accessing particular segments or fields by omission of those segments or fields from the logical database. Sensitivity is implemented through the DB PCB.
sequence
A user-defined object that generates a sequence of numeric values according to user specifications.
sequence field
The field in a database segment that used to store segment occurrences in sequential ascending order. Also called a key field.
sequential buffering (SB)
Efficient sequential input buffering techniques that reduce the elapsed time required to sequentially process large IMS OSAM databases.
sequential data set
A non-DB2 data set whose records are organized on the basis of their successive physical positions, such as on magnetic tape. Several of the DB2 database utilities require sequential data sets.
sequential dependent segment (SDEP)
A segment of a data entry database that is chained off the root segment and inserted (last-in first-out) into the last part of a DEDB area. After being inserted by an online program, the SDEP cannot be modified.
sequential prefetch
A mechanism that triggers consecutive asynchronous I/O operations. Pages are fetched before they are required, and several pages are read with a single I/O operation.
sequential read
A set of several consecutive blocks that are read with a single read I/O operation. Sequential reads are issued by the Sequential Buffering (SB) component of IMS in order to reduce the elapsed time required to sequentially process large IMS OSAM databases.
serialized profile
A Java object that contains SQL statements and descriptions of host variables. The SQLJ translator produces a serialized profile for each connection context.
server
The target of a request from a remote requester. In the DB2 environment, the server function is provided by the distributed data facility, which is used to access DB2 data from remote applications.
service class
An eight-character identifier that is used by the z/OS Workload Manager to associate user performance goals with a particular DDF thread or stored procedure. A service class is also used to classify work on parallelism assistants.
service elements
The discrete hardware and software products that provide a terminal user with processing ability.
service group
In an RSR environment, a collection of all IMSs that access RSR-covered databases at an active or at a remote site, including the RECON data set. A service group usually includes one or more IMSs at a single site, with the databases and RECON data set shared between the IMSs.
service request block
Start of changeA unit of work that is scheduled to execute.End of change
session
A link between two nodes in a VTAM network.
session protocols
The available set of SNA communication requests and responses.
session recovery
The XRF process in which IMS switches primary sessions on class 1 terminals to backup sessions or reestablishes service on class 2 terminals during takeover.
Start of changeset operatorEnd of change
Start of changeThe SQL operators UNION, EXCEPT, and INTERSECT corresponding to the relational operators union, difference, and intersection. A set operator derives a result table by combining two other result tables. End of change
SG
See service group.
shadow database
In an RSR environment, a database maintained at the tracking site as a remote copy of a database at the active site. If a remote takeover occurs, the shadow database becomes the master database.
shared communications area (SCA)
A coupling facility list structure that a DB2 data sharing group uses for inter-DB2 communication.
shared index database
A secondary index database containing more than one secondary index in the same physical operating system data set.
shared queue
A collection of data objects with the same name that reside on a coupling facility queue structure. Data objects on a shared queue are available to all CQS clients that have access to the structure. See also message queue.
share levels
When you register a database to the Data Base Recovery Control (DBRC), you assign to the database one of four share levels: level zero, level one, level two, or level three.
share lock
A lock that prevents concurrently executing application processes from changing data, but not from reading data. Contrast with exclusive lock.
sharing complex
A group of subsystems using IMS and DBRC that share the same RECON data sets. Also called data sharing complex.
shift-in character
A special control character (X'0F') that is used in EBCDIC systems to denote that the subsequent bytes represent SBCS characters. See also shift-out character.
shift-out character
A special control character (X'0E') that is used in EBCDIC systems to denote that the subsequent bytes, up to the next shift-in control character, represent DBCS characters. See also shift-in character.
SHISAM
See simple HISAM.
SHSAM
See simple hierarchic sequential access method.
sibling segments
Two or more occurrences of different sibling segment types having a common parent segment occurrence.
sibling segment types
Two or more segment types having a common parent segment type. Contrast with twin segments.
significant data
IMS state data that keeps a resource from being deleted in RM when the resource is no longer active on any IMS. This term was introduced by ETO, when deciding whether status was significant enough to prevent the dynamic control block from being deleted when the user signed off or the node logged off. See also state data.
significant status
A resource status classified as significant. In addition to being recoverable, if the resource status is specified as significant, the resource cannot be deleted after a terminal logoff, a user signoff, or an IMS restart.
signoff
The act a terminal user performs in order to end an identification of a user to IMS. When the terminal is an ETO terminal, the signoff process usually disconnects the user structure from the terminal structure and deletes the user structure.
sign-on
For DB2 A request that is made on behalf of an individual CICS or IMS application process by an attachment facility to enable DB2 to verify that it is authorized to use DB2 resources.
For IMS The act a terminal user performs in order to identify a user to IMS. When the terminal is an ETO terminal, the signon process also creates a user structure and connects the user structure to the terminal structure.
signon verification
The verification of a user ID that takes place at signon. Signon verification is required before a user can access protected IMS resources.
simple checkpoint
The periodic recording of control information and system status on the system log at user-specified intervals.
simple hierarchic sequential access method (SHSAM)
A type of HSAM database that contains only root segments, which have no prefixes.
simple HISAM
The support for a HISAM database that contains only one segment type.
simple page set
A nonpartitioned page set. A simple page set initially consists of a single data set (page set piece). If and when that data set is extended to 2 GB, another data set is created, and so on, up to a total of 32 data sets. DB2 considers the data sets to be a single contiguous linear address space containing a maximum of 64 GB. Data is stored in the next available location within this address space without regard to any partitioning scheme.
simple table space
Start of changeA table space that is neither partitioned nor segmented. Creation of simple table spaces is not supported in DB2 Version 9.1 for z/OS</