Oracle Database Administration: The Essential Refe

Specifying Hints

Here’s the rub: for all its advances, the cost-based optimizer still may not find the best access path. For years, developers and DBAs were used to rewriting queries to ensure that the rule-based optimizer would use the most efficient path. You cannot do this with the cost-based optimizer. However, you can provide hints to the cost-based optimizer, giving additional information and guidelines on how to do the best optimization.