DB2 10.5 for Linux, UNIX, and Windows
DB2 10.5 for Linux, UNIX, and Windows
This parameter is used by the query optimizer to help estimate how much buffer pool space will be available at run time for the access plan chosen.
Recommendation: When running the DB2 database product in a multi-user environment, particularly with complex queries and a large buffer pool, you might want the query optimizer to know that multiple query users are using your system so that the optimizer should be more conservative in assumptions of buffer pool availability.
When this parameter is set to AUTOMATIC, the parameter is updated to an appropriate value immediately, when the database configuration file is created, or when the database configuration file is reset.
Setting this parameter might help the optimizer model buffer pool usage more accurately. If you set this parameter manually, begin with a value of 2, regardless of the average number of applications that you run. After you assess the behavior of the optimizer and test the performance of your application at this setting, you can increase the value of the parameter in small increments. Continue to assess the behavior of the optimizer and test the performance of your application each time you increase the value of the parameter. Setting this parameter to a value that is too high might cause the optimizer to underestimate the amount of buffer pool space that is available to the query.
After you change the value of this parameter, consider rebinding applications by using the REBIND PACKAGE command.