IBM® Informix® 12.10
What optimizer directives are
Optimizer directives are specifications formatted as comments that provide information to the query optimizer about how to execute a query.
You can use two kinds of optimizer directives:
- Optimizer directives in the form of instructions that are embedded in queries (For more information, see Optimizer directives that are embedded in queries.
- External optimizer directives that you create and save for use as temporary workaround solutions to problems when you do not want to change SQL statements in queries. (For more information, see External optimizer directives.)