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
- 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 description)
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