Purpose
Influences the maximum number of tables that can be joined per query block.
Field Group
Performance
Valid Settings
0, and 64 through 128
Zero means MaxJoinTables will use the system default upper limit of 128.
Default
0
Changes Take Effect
After the DBS Control Record has been written.
Usage Notes
MaxJoinTables sets a system-wide upper bound on the MaxJoinTables cost parameter used during optimization. The value 0 is mapped internally to 128.
The actual maximum number of join tables in a query block is determined by both this field, and by the MaxJoinTables configuration setting in the Optimizer cost profile.
If the RevertJoinPlanning DBS Control field is set to TRUE, or if the RevertJoinPlanning configuration setting for the cost profile is set to TRUE, the maximum join tables is 64, regardless of the MaxJoinTables setting.
Related Topics
| For more information on… | See… |
|---|---|
| RevertJoinPlanning | RevertJoinPlanning. |
| join planning, optimization, and cost profiles, | SQL Request and Transaction Processing. |
| database limits | SQL Fundamentals. |