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Shared Memory

In This Chapter
Shared Memory
Shared-Memory Use
Shared-Memory Allocation
Shared-Memory Size
Action to Take If SHMTOTAL Is Exceeded
Processes That Attach to Shared Memory
How a Client Attaches to the Communications Portion
How Utilities Attach to Shared Memory
How Virtual Processors Attach to Shared Memory
Defining a Unique Key Value
Specifying Where to Attach the First Shared-Memory Segment
Attaching Additional Shared-Memory Segments
Defining the Shared-Memory Lower-Boundary Address
Resident Shared-Memory Segments
Resident Portion of Shared Memory
Shared-Memory Header
Shared-Memory Buffer Pool
Buffer Overflow to the Virtual Portion
Buffer Size
Configurable Page Size
Logical-Log Buffer
Physical-Log Buffer
Lock Table
Virtual Portion of Shared Memory
Management of the Virtual Portion of Shared Memory
Size of the Virtual Portion of Shared Memory
Components of the Virtual Portion of Shared Memory
Shared-Memory Internal Tables
Big Buffers
Session Data
Thread Data
Dictionary Cache
Sorting Memory
SPL Routine Cache
Global Pool
Communications Portion of Shared Memory
Concurrency Control
Shared-Memory Mutexes
Shared-Memory Buffer Locks
Types of Buffer Locks
Database Server Thread Access to Shared Buffers
LRU Queues
Components of LRU Queue
Pages in Least-Recently Used Order
LRU Queues and Buffer-Pool Management
Number of LRU Queues to Configure
Number of Cleaners to Allocate
Number of Pages Added to the MLRU Queues
End of MLRU Cleaning
Configuring the Database Server to Read Ahead
Database Server Thread Access to Buffer Pages
Identify the Page
Determine the Level of Lock Access
Try to Locate the Page in Shared Memory
Locate a Buffer and Read Page from Disk
Lock the Buffer If Necessary
Release the Buffer Lock and Wake a Waiting Thread
Flushing Data to Disk
Events That Prompt Flushing of Buffer-Pool Buffers
Flushing Before-Images First
Flushing the Physical-Log Buffer
Events That Prompt Flushing of the Physical-Log Buffer
When the Physical-Log Buffer Becomes Full
Synchronizing Buffer Flushing
Ensuring That Physical-Log Buffers Are Flushed First
Flushing the Shared-Memory Pool Buffer
Describing Flushing Activity
Foreground Write
LRU Write
Chunk Write
Flushing the Logical-Log Buffer
When the Logical-Log Buffer Becomes Full
After a Transaction Is Prepared or Terminated in a Database with Unbuffered Logging
When a Session That Uses Nonlogging Databases or Unbuffered Logging Terminates
When a Checkpoint Occurs
When a Page Is Modified That Does Not Require a Before-Image in the Physical-Log File
Buffering Simple-Large-Object Data Types
Blobpages Do Not Pass Through Shared Memory
TEXT and BYTE Objects Are Created Before the Data Row Is Inserted
Tracking Blobpages
Memory Use on 64-Bit Platforms
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