Articles & Content


Why did the optimizer choose that path? (Part 1 of 2) (A14)

Topic: 2006 EU

Subtopic: DB2 for z/OS

DATE: 2006-10-5 (09:00 - 10:00)
SPEAKERS: Terry Purcell (IBM Silicon Valley Lab)

Ever wondered why the DB2 optimizer chooses a certain access path? The wrong index, poor table join sequence? Before DB2 V8, you had to be an optimizer expert to answer that question. This presentation will outline a method to utilize the extensive access path detail available with V8 Visual Explain and compare with the actual reality for a given query.

EXP. LEVEL: Beginner,Intermediate,Advanced


Query problems

Query breakdown

Comparing estimates with reality

What to do if the estimate is incorrect?

Automating the process

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