Customizing the Coserver Definition

You can customize coservers by adding parameter definitions to the coserver definition. Any parameters added to the coserver definition override the global configuration for that coserver.

Specifying Coserver-Specific Configuration

Figure 8 shows the global ONCONFIG parameters that apply to all coservers but that you can override in the coserver-specific sections.

ROOTSLICE       rootdbs 
ROOTPATH        /informixdata/rootchk%c 
ROOTOFFSET      0               
ROOTSIZE        11000           
PHYSSLICE       physslice       
PHYSFILE        10000           
LOGFILES        20             
LOGSIZE         1024            
LOCKS           4096
BUFFERS         5000
SHMVIRTSIZE     32768       
SHMADD          16384

You can override the following global parameters in the coserver definition:

• ROOTNAME

  Whether or not you use ROOTSLICE to generate root dbspaces on each coserver, you can use ROOTNAME in each coserver definition to specify the root dbspace chunk. The names must be unique across all the coservers. To do this, see "Formatting Characters in ROOTPATH and MIRRORPATH" in the IBM Informix: Extended Parallel Server Administrator's Guide.

  For example, because specific-purpose coservers contain only unlogged data, you might specify smaller root dbspaces for these coservers.

  Tip:
  To simplify managing fully capable coservers, instead of specifying individual root dbspaces, create logslices to contain the logical log files and set the global configuration parameters ROOTSLICE and PHYSLICE. For more information about logslices, see the IBM Informix: Extended Parallel Server Administrator's Guide and the IBM Informix: Administrator's Reference.
• ROOTPATH and MIRRORPATH

  Specifies the location of the primary (and mirror) chunk of the root dbspace

  These parameters can contain formatting characters.

• ROOTSIZE

  Specifies the size (in KB) of the initial primary chunk assigned to the root dbspace

• ROOTOFFSET and MIRROROFFSET

  Specifies the offset of the primary and mirror chunk of the root dbspace

• PHYSDBS

  Specifies the location of the physical log

  You can specify a different dbspace and PHYSFILE as well.

• LOCKS

  Specifies the number of locks

  Because COMPUTE and TEMPDATA coservers do not host permanent tables, they do not require as many locks as fully capable coservers.

• BUFFERS

  Specifies the number of buffers

  By default, the BUFFERS setting for specific-purpose coservers is 20 percent of the global BUFFERS parameter in the ONCONFIG file. If the global BUFFERS parameter is not specified, the minimum of 100 buffers is the default.

• SHMVIRTSIZE and SHMADD

  Specifies the size of the virtual memory segment

  Specific-purpose coservers might use less memory than fully capable coservers and might need to add memory in smaller increments. The default setting for SHMVIRTSIZE on a specific-purpose coserver is 20 percent of the global SHMVIRTSIZE setting.

To customize a coserver, override the global configuration parameters by adding parameters and settings between the COSERVER and END parameters in the coserver-specific section of the ONCONFIG file.

Figure 9 shows the coserver-configuration section for each coserver. One of the specific-purpose coservers is configured with both the COMPUTE and TEMPDATA capabilities. The fully capable coservers on nodes able, baker, and charlie use the global parameters. The specific-purpose coservers on nodes delta and echo specify smaller memory and lock parameters and a larger root dbspace because the root dbspace contains the logical and physical log files.

COSERVER        1
NODE            able
END

COSERVER        2
NODE            baker
END

COSERVER        3            
NODE            charlie
END

COSERVER        4
NODE            delta
CAPABILITIES    COMPUTE
ROOTSIZE        40000           
PHYSDBS         rootdbs.4
LOCKS           2000            
BUFFERS         100            
SHMVIRTSIZE     8192          
SHMADD          8192            
END

COSERVER        5
NODE            echo
CAPABILITIES    COMPUTE,TEMPDATA
ROOTSIZE        40000           
PHYSDBS         rootdbs.5
LOCKS           2000           
BUFFERS         100            
SHMVIRTSIZE     8192           
SHMADD          8192            
END

Specifying a Specific Purpose for a Coserver

The CAPABILITIES configuration parameter specifies the specific use of the coserver in the COSERVER definition section for a new coserver. If the CAPABILITIES parameter is omitted, the added coserver is a fully capable coserver that can host permanent data and perform all coserver tasks.

To add a specific-purpose coserver that can perform only specified processing tasks and host temporary files, include the CAPABILITIES parameter.

onconfig.std value

None

if not present

The coserver is fully capable.

units

COMPUTE: capability performs compute operations such as aggregation, joins, and sorts, and stores the overflow from these operations in TEMP dbspaces that you create.

TEMPDATA: capability stores temporary user tables in TEMP dbspaces that you create.

separators

Comma or colon (no white spaces)

range of values

COMPUTE
TEMPDATA
COMPUTE,TEMPDATA

takes effect

When shared memory is initialized

refer to

Your IBM Informix: Performance Guide for information about appropriate settings

The types of specific-purpose coservers are: COMPUTE and TEMPDATA. You can specify both COMPUTE and TEMPDATA as arguments to the CAPABILITIES parameter.

Specific-purpose coservers create their root dbspaces when they are initialized, but you need to create TEMP dbspaces for temporary tables and the overflow of query operators.

Creating Storage Spaces for Coservers

For each coserver that you add, you must create dbspaces or dbslices that add dbspaces to these coservers.

For example, if you create cogroup_tempspace to include all specific-purpose coservers and create raw devices with the path /dbspaces/temp.4 and so on, you might use the following onutil command to create a temporary dbslice:

onutil CREATE TEMP DBSLICE spec_temp1 FROM cogroup_tempspace 
CHUNK \"/dbspaces/temp.%c\" SIZE 490000; 

If you specified the ROOTSLICE global configuration parameter, the database server automatically creates uniformly named root dbspaces for each of your coservers. If you do not specify the ROOTSLICE configuration parameter, you define a root dbspace by setting a unique value for the ROOTNAME configuration parameter in each coserver definition.

In addition, you must create dbspaces:

• For fully capable coservers, add both standard and temporary dbspaces.
• For specific-purpose coservers, you must create at least one temporary dbspace.
  • COMPUTE coservers require a temporary dbspace for query operator overflow.
  • TEMPDATA coservers require temporary dbspaces to manage temporary tables written to that coserver.

For information on defining disk space and creating dbspaces and dbslices, refer to your IBM Informix: Administrator's Guide.