Query Optimizer Documentation
The job of the Optimizer is to determine the best execution plan for each SQL statement. An overview of the Optimizer, uses of the Optimizer, Optimizer components, access paths, Optimizer statistics and Optimizer hints can be found in Database Concepts. More documentation specific to query Optimizer fundamentals, Optimizer statistics and Optimizer controls can be found in the SQL Tuning Guide. Documentation specific to the Optimizer is also available in the Database Performance Tuning Guide.