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Hint, Don't "Trick", Your Troublesome Access Paths (B06)

Topic: 2005 NA

Subtopic: DB2 for z/OS



DATE: 2005-05-24 (10:00 AM - 11:10 AM)
SPEAKERS: Terry Berman (DST Systems Inc.)

The DB2 Optimizer cannot (even with "good" Stats) produce optimum access paths 100% of the time, nor rule out occasional, detrimental switches on REBINDs. SQL "Tricks" and "Fake" Stats can manipulate access paths, but are limited and introduce side-effects. DB2 OPTHINT is a direct and effective method, but is difficult to use. We show simple REXX automation that has made Optimizer Hints the production choice at DST.

EXP. LEVEL: Intermediate,Advanced

OBJECTIVES:

Good Stats, "Bad" Access Paths and Switches

SQL "Tricks" and "Fake" Stats: cost vs. benefit

Optimizer Hints, as DB2 implements them

DSTHINT: Automation for Optimizer Hints

Production experiences



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