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Improved EDM Pool Management in DB2 12

April 18, 2017

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

EDM pool sizes are set during the installation process by using the install clist to set these parms: DB2 12 provides some improvements in the way EDM pool memory is managed. Prior to DB2 12, the EDM pool zparms could be increased in size, but they couldn't be decreased below the level of the values specified at installation time. However, DB2 12 only allocates storage for these pools when it's needed. So rather than allocate all of the memory up front for the given pools, DB2 will wait until a request for storage. In addition, unused structures are released in DB2 12, a feature that helps keep the allocated storage size below the maximum set values.

The upshot is that, because DB2 will free unused storage using an LRU algorithm, you shouldn't encounter a storage failure should the required storage exceed a given limit.

Posted April 18, 2017| Permalink