DB2 Server for VSE: System Administration

Estimating Storage Pool Requirements

For estimating storage pool sizes, you need to estimate:

• The size of used portions of dbspaces. This includes tables, indexes, and free space on used dbspace pages.
• Shadow paging requirements. This is an estimate of the number of dbspace pages that can change between checkpoints.

To estimate the number of pages required for a storage pool use the following formula:

Pool pages = 8 x Number of dbspaces
            + 1.5 x Data pages for all dbspaces in the pool
            + Data pages for the largest table in the pool

This calculation covers header pages and pages required for table rows and indexes on those tables. If you have increased your dbspace data pages value to accommodate future growth of tables, you can decrease the pool pages correspondingly.

The addition of the factor of data pages for the largest table in the pool should accommodate storage pool demands for shadow paging. This allows for UNLOAD and RELOAD of the largest table in the storage pool.