Applying changes to a Db2 subsystem

You can use the Db2® Commands feature of Db2 Performance Expert (for the ALTER BUFFERPOOL commands).

About this task

To apply the SQL statements, you can copy them to SPUFI, or you can run them via Db2 Connect. Additionally, consider the following tips when you are going to apply the proposed changes:

If you see a buffer pool size set to zero in the optimization result, double-check that this buffer pool is no longer used. Consider the eventuality that this buffer pool did not show any activity during the data collection time, but an unused object can become active under certain circumstances.
If possible, you should stop the database before applying the changes, especially in a data sharing environment. Also consider applying the changes during planned outages.
If the virtual buffer pool size is limited, or the proposed size is less than the original size, you should first apply the changes that reduce the sizes of buffer pools, then apply the changes that increase the sizes of buffer pools. The opposite order can result in insufficient virtual storage. However, buffer pools are not always freed immediately. Db2 reduces the sizes of buffer pools by first identifying buffers that are to be deleted. That means, those buffers cannot be used again. Db2 releases buffers immediately or at a later moment, whatever is more appropriate. Therefore, it is good practice to ensure that buffers have actually been released before enlarging buffer pools.
After applying the ALTER INDEX and ALTER TABLESPACE statements, the reassignments of objects to different buffer pools remain pending until Db2 happens to close and reopen the data sets of the changed page sets, which depends on several parameters. If immediate reassignments are required, you need to stop and start the database.

For details about the Db2 command ALTER BUFFERPOOL see the IBM Db2 11 for z/OS: Command Reference.
For details about the SQL statements ALTER and CREATE see the IBM Db2 11 for z/OS: SQL Reference.