Allocating buffer pool storage to avoid paging

Paging occurs when the virtual storage requirements for a buffer pool exceed the real storage capacity for the z/OS® image. In this case, the least recently used data pages in the buffer pool are migrated to auxiliary storage. Subsequent access to these pages results in a page fault, and the page must be brought into real storage from auxiliary storage. Paging of buffer pool storage can negatively affect Db2 performance. The statistics for PAGE-INS REQUIRED FOR WRITE and PAGE-INS REQUIRED FOR READ in the IBM® OMEGAMON® for Db2 Performance Expert on z/OS statistics report are useful in determining if the buffer pool size setting is too large for available real storage.

If the amount of virtual storage that is allocated to buffer pools is more than twice the amount of real storage, you cannot increase the buffer pool size. Db2 allocates the minimum buffer pool storage for the BP0, BP8K0, BP16K0, and BP32K buffer pools as shown in the following table.