Articles & Content


Who Stole My Favorite Scan and Access Path ? (G16)

Topic: 2008 EU

Subtopic: DB2 for z/OS

DATE: 2008-10-16 (11:45 - 12:45)
SPEAKERS: Steen Rasmussen (CA)

During the lifetime of DB2, Explain and Access Path prediction have gone through a huge evolution. This presentation will look at some of the major changes over time and how the Optimizer has grown from a toddler to a much more robust piece of art. Performance is a major concern for all DB2 sites, so we will look into different methods to predict performance before doing Bind and Rebind, which potential corrective actions to take and how to prepare yourself to find the reason(s) for a better or worse access path when "something slipped through".

EXP. LEVEL: Beginner,Intermediate


Explain evolution over the years - are you aware of all the new stuff.

Optimizer resources for deciding "the correct" access path and how the user can influence these decisions.

Which methods can be used to make corrective actions to application SQL and how to predict access path when moved to the next stage/level.

Explain versioning and the information needed in order to find the reason(s) for a access path change or performance degradation/improvement.

A method to compare access path and performance improvement/degradation (the cost of executing the SQL statement) and a potential Rebind.

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