Articles & Content


Why did the Optimizer choose that Access Path? (A10)

Topic: DB2 for z/OS

Subtopic: 2010

DATE: 2010-5-13 (09:45 AM - 10:45 AM)
SPEAKERS: Terry Purcell (IBM)

The wrong index, or a poor table join sequence? This presentation 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.

EXP. LEVEL: Beginner,Intermediate,Advanced


Identify reasons why the optimizer can choose a poor access path.

Present a method to identify why the optimizer has chosen a poor access path given sample queries.

Identify and evaluate solutions for each query performance challenge.

Breakdown the complexity of the DB2 for z/OS optimizer into logical components for attendees to understand.

Have some fun along the way.

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