Articles & Content


Why did the DB2 for z/OS Optimizer choose that Access Path? (B08)

Topic: 2011 NA

Subtopic: DB2 for z/OS

DATE: 2011-5-4 (02:45 PM - 03:45 PM)
SPEAKERS: Terry Purcell (Ibm Silicon Valley Lab ), Saghi Amirsoleymani (Ibm Silicon Valley Lab )

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.

EXP. LEVEL: Intermediate,Advanced


An understanding of the logical components of the DB2 for z/OS optimizer

How to identify reasons why the optimizer can choose a poor access path.

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

How to identify and evaluate solutions for each query performance challenge

How Optim Query Tuning Solutions can help make you more productive by providing appropriate visualization, access path comparison capabilities, and advisor recommendations

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