IBM BPM, V8.0.1, All platforms > Tuning > Advanced tuning > Database: DB2 for z/OS specific tuning
Set buffer pool sizes correctly
A buffer pool is an area of memory into which database pages are read, modified, and held during processing. Buffer pools improve database performance.
If a needed page of data is already in the buffer pool, that page is accessed faster than if the page has to be read directly from disk. As a result, the size of the DB2 buffer pools is critical to performance.
The amount of memory used by a buffer pool depends on two factors: the size of buffer pool pages and the number of pages allocated. Buffer pool page size is fixed at creation time and can be set to 4, 8, 16 or 32 KB.
The buffer pools must coexist with other data structures and applications, all without exhausting available memory and causing paging to occur. In general, having larger buffer pools improves performance up to a point by reducing I/O activity. Beyond that point, allocating additional memory no longer improves performance. To choose appropriate buffer pool size settings, monitor the buffer pool hit ratio by using DB2 database tools, or by using the DB2 display buffer pool command. Avoid configuring large buffer pool size settings, which lead to paging activity on the system.