EDM storage

The environmental descriptor manager (EDM) pools contain skeleton application plans and packages, database descriptors, and cached dynamic SQL statements.

EDM storage is composed of the following components, each of which is in a separate storage area:

EDM DBD pool
An above-the-bar pool that contains database descriptors (DBDs)
EDM statement pool
An above-the-bar pool that contains dynamic cached statements
EDM skeleton pool
An above-the-bar pool that contains skeleton package tables (SKPTs) and skeleton cursor tables (SKCTs)
During the installation process, the DSNTINST CLIST calculates the sizes of the following types of storage:
  • EDM statement cache
  • EDM DBD cache
  • EDM skeleton pool
You can check the calculated sizes on the DSNTIPC installation panel.

For data sharing, you might need to increase the EDM DBD cache storage estimate to compensate for the need to store multiple concurrent DBD copies. Each member maintains a separate copy of a DBD that is referenced by multiple members. New and separate references to the same DBD might result in multiple copies being loaded while invalidated copies remain, until the threads that use them are either committed or deallocated.

Because of an internal process that changes the size of plans initially bound in one release and then are rebound in a later release, you should carefully monitor the sizes of the EDM storage pools, and increase their sizes, if necessary.