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Tuning Access Paths: Red Flags to Look for (G08)

Topic: DB2 for z/OS

Subtopic: 2007



DATE: 2007-5-8 (04:20 PM - 05:20 PM)
SPEAKERS: Joseph Burns (Highmark, Inc.)

As DBAs and application developers we have all had to look at an access path at one time or another. Sometimes a performance issue can be easily seen in the access path, but other times it can be a little more difficult to spot. This is especially true when dealing with explain output that generates multiple query blocks. In this session we will look at explain output and highlight key areas that affect the performance of various SQL statements such as joins, sorts and subqueries. The intent is to focus our efforts on the pieces of the access path that have the most impact on the performance of our SQL.

EXP. LEVEL: Intermediate

OBJECTIVES:

Gain a general understanding of key plan table columns

Understand the difference between Sequential and List Prefetch

Understand key performance characteristics of Nested loop and Merge Scan joins

Understand key performance characteristics of Correlated and Non-Correlated subqueries

Gain insight into correcting common access path issues



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