Defining Cogroups

Define cogroups to facilitate the management of multiple coservers in Extended Parallel Server. A cogroup is a set of coservers within the database server. You assign coservers to cogroups in order to manage them as a unit. Typically, you assign coservers that share tables to the same cogroup. A coserver can be a member of multiple cogroups.

Extended Parallel Server provides a system-defined cogroup that is called cogroup_all. The cogroup_all cogroup includes all the coservers that the ONCONFIG configuration file defines.

You might want to define a cogroup that consists of a subset of the coservers for a specific application or database.

To define a cogroup

Determine which coservers should be part of the cogroup.
Obtain the coserver names from your ONCONFIG configuration file. The coserver name has the following format:
```
dbservername.coserver-number
```
For dbservername, use the value of the DBSERVERNAME configuration parameter.

For coserver-number, use the value of the COSERVER configuration parameter.

For example, your ONCONFIG file defines 16 coservers as follows:
```
DBSERVERNAME               eds
...
COSERVER               1
   NODE                     octopus1
   ...
   END
...
COSERVER               16
   NODE               bear16
   ...
END
```
The coserver names are eds.1, eds.2, and so forth. For more information see Coserver-Specific Configuration Parameters.
Use the onutil command-line utility to create the cogroup.
The following example shows onutil running with interactive input. The input is the onutil CREATE COGROUP command to create a cogroup that includes the first four coservers in the preceding sample ONCONFIG configuration file.
```
%onutil
1> CREATE COGROUP acctg_group
2> from eds.1, eds.2, eds.3, eds.4;
Cogroup successfully created.
3> QUIT;
```
For more information about the onutil CREATE COGROUP command, see the utilities chapter in the IBM Informix: Administrator's Reference.