Support for collection of more accurate real storage usage statistics

by Akiko Hoshikawa and Judy Tobias

In Db2 11 for z/OS and Db2 12 for z/OS, we introduce an enhancement that improves your ability to obtain accurate real storage usage statistics. In the past, z/OS capacity planners have experienced difficulties in determining an accurate estimate of the main memory that their Db2 subsystems used. With this enhancement, you can have more confidence that you are acquiring the appropriate amount of main memory for your Db2 environment.

When you enable this enhancement, Db2 writes new fields in IFCID 225 trace records during the first statistics interval after midnight each day. Those fields contain the number of discarded pages that are eligible for page steal. You can use those statistics in conjunction with existing real storage usage fields to calculate accurate storage usage. By examining daily storage statistics for multiple weeks, you can discover trends in your real storage usage.

 

You might see a performance impact during the time that the new statistics are collected. For that reason, this enhancement is not automatically enabled when you apply the associated PTF. To avoid unexpected side effects, you might want to enable this enhancement in collaboration with IBM Software Support.

 

Related information

Base release enhancements after the DB2 12 initial release (see "Support for collection of more accurate real storage usage statistics")

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