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DB2® for z/OS® Version 8 DBA Certification Guide by Susan Lawson

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Chapter 17. SQL Optimization and Performance

• Access paths and optimization

• Designing indexes and SQL for performance

Tuning DB2 queries is critical to performance. You need to understand how the DB2 optimizer works and how to create the best possible indexes for your queries. You also need to know how to determine whether DB2 is using that index and whether it is performing joins and other operations effectively by using the various tools available.

Access Paths and Optimization

If you want to know how DB2 will execute a query, you must analyze its access path, which is the method for retrieving data from a specific table or set of tables. Oftentimes, unexpected decreases in performance, such as excessive GETPAGEs, can be attributed to a ...

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