Articles & Content


Why did the DB2 for z/OS Optimizer Choose that Access Path? (A06)

Topic: 2011 AU

Subtopic: DB2 for z/OS

The wrong index, or a poor table join sequence? Terry Purcell, from the DB2 for z/OS optimizer team and highly popular speaker, will outline a systematic method to identify and resolve query performance issues.
The method utilizes extensive access path detail already available for a query.
We determine what the optimizer "sees" and compare it to the actual reality. The key to providing the best solution for a poor access path choice is dependent on understanding why the poor choice was made.
We will also enumerate common challenges that the optimizer faces with choosing the best path for your SQL, and the most appropriate solution for each case.
IBM Optim Tuning solutions will be used to illustrate some of these concepts.

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