Virtual storage requirements for storage pools and working storage

During the ISPF tailoring session, you specify values that the DSNTINST CLIST uses to calculate main storage size.

Recommendation: Determine these values based on your estimated application workload before you install or migrate Db2.

These values provide an estimate of the private area that is needed by the database services address space (ssnmDBM1), the largest of the Db2 address spaces. If the estimated virtual storage for the address space is not available, you can re-evaluate the sizes that you requested.

The calculations in this topic are planning estimates. The noted values do not provide the exact limits, but they indicate a reasonable range of values.

The sum of the following values must fit the region size that Db2 supports:
  • VSAM data set control block storage size
  • Working storage size

The CLIST adds a fixed code size to the sum of these values to determine the main storage size.

After you specify the values listed above, the CLIST determines the EDM pool size and the size that is needed for the data set control blocks. The CLIST adds the working storage size and the fixed code size to update the region size that is used in the Db2 startup procedures. The CLIST also displays this information on CLIST calculations panel 1: DSNTIPC.

Use the formulas in this topic to estimate your storage needs. For your reference, the default values are included where appropriate.