Fixing a buffer pool in real storage

You can use the PGFIX keyword with the ALTER BUFFERPOOL command to fix a buffer pool in real storage for an extended period of time.

About this task

The PGFIX keyword has the following options:

PGFIX(YES): The buffer pool is fixed in real storage for the long term. Page buffers are fixed when they are first used and remain fixed.
PGFIX(NO): The buffer pool is fixed in real storage only for the duration of an I/O operation. Page buffers are fixed and unfixed in real storage, allowing for paging to disk. PGFIX(NO) is the default option.

To prevent PGFIX(YES) buffer pools from exceeding the real storage capacity, DB2® uses an 80% threshold when allocating PGFIX(YES) buffer pools. If the threshold is exceeded, DB2 overrides the PGFIX(YES) option with PGFIX(NO).

Procedure

To fix a buffer pool in real storage:

Issue an ALTER BUFFERPOOL command and specify PGFIX(YES). Use PGFIX(YES) for buffer pools that have a high I/O rate, those buffer pools with a high number of pages read or written. For buffer pools with zero I/O, such as some read-only data or some indexes with a nearly 100% hit ratio, PGFIX(YES) is not recommended because it does not provide any performance advantage.