IBM Books

Administration Guide

Chapter 13. Understanding the SQL Compiler

When an SQL query is compiled, a number of steps are performed before the "best" access plan is either executed or written to the system catalog tables containing information about application packages.

In a partitioned database environment, all of the work done on a SQL query by the SQL Compiler takes place at the database partition to which you connect. Once the executable access plan is created, the compiled query is distributed to all database partitions in the database.

The following topics provide more information about the steps performed by the SQL Compiler:

The following sections also provide information about factors external to the compiler which can affect the results produced by the compiler:

Chapter 14. "SQL Explain Facility" describes how you can examine the access plan chosen by the SQL compiler.

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