- Configuration Type
- Database
- Parameter Type
- Configurable
- Default [Range]
- 5 [ 0 - 9 ]
- Unit of Measurement
- Query Optimization Class (see below)
The query optimization class is used to direct the optimizer to use
different degrees of optimization when compiling SQL queries. This
parameter provides additional flexibility by setting the default query
optimization class used when neither the SET CURRENT QUERY OPTIMIZATION
statement nor the QUERYOPT bind command are used.
The query optimization classes currently defined are:
- 0 - minimal query optimization.
- 1 - roughly comparable to DB2 Version 1.
- 2 - slight optimization. Specifies a level of optimization higher
than that of Version 1, but at significantly less optimization cost than
levels 3 and above, especially for very complex queries.
- 3 - moderate query optimization.
- 5 - significant query optimization with heuristics to limit the effort
expended on selecting an access plan. This is the default.
- 7 - significant query optimization.
- 9 - maximal query optimization