Enabling automatic buffer pool size management

You can reduce the amount of time that you spend monitoring and adjusting buffer pools by enabling the DB2® automatic buffer pool size management feature.

About this task

Automatic buffer pool management does not completely replace existing tools to configure, monitor, and tune buffer pool size. However, when you have initially sized your buffer pools, DB2 and WLM can fine tune the buffer pool size, based on long term trends and steady state growth. The DISPLAY BUFFERPOOL output includes an AUTOSIZE attribute. You can enable or disable automatic buffer pool management at the individual buffer pool level. Automatic buffer pool management is off by default.

Procedure

To enable automatic buffer pool size management:

Issue an ALTER BUFFERPOOL command and specify the AUTOSIZE(YES) option. DB2 performs dynamic buffer pool size adjustments that are based on real-time workload monitoring.

Start of change When you enable automatic buffer pool management, DB2 reports the buffer pool size and hit ratio for random reads to the z/OS® Workload Manager (WLM) component, and automatically increases buffer pool size, as appropriate, by as much as 25% of the originally allocated size. End of change

Start of change Whenever the size of a buffer pool is increased, the increased size becomes the new size of the buffer pool. After the buffer pool is deallocated and reallocated, it becomes eligible to be increased by as much as 25% of the new size. End of change

What to do next

Because automatic buffer pool management only increases the size of buffer pools, you might need to sometimes manually reduce the size of a buffer pool that has become too large.