The query optimization class is used to direct the optimizer
to use different degrees of optimization when compiling SQL and XQuery
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 option on the BIND command are used.
- Configuration type
- Database
- Parameter type
- Configurable online
- Configurable by member in a DB2® pureScale® environment
- Propagation class
- Connection
- Default [range]
- 5 [ 0 - 9 ]
Note: The default value is subject to change by the DB2 Configuration Advisor after
initial database creation.
- Unit of measure
- Query Optimization Class (see the following list)
The query optimization classes currently defined
are:
- 0 - minimal query optimization.
- 1 - roughly comparable to DB2 Version 1.
- 2 - slight optimization.
- 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