MAX DEGREE field (PARAMDEG subsystem parameter)
The PARAMDEG subsystem parameter specifies the maximum degree of parallelism for a parallel group. When you specify a non-zero value for this parameter, you limit the degree of parallelism so that Db2 cannot create too many parallel tasks that use virtual storage.
| Acceptable values: | 0–254 |
|---|---|
| Default: | 0 |
| Update: | option 30 on panel DSNTIPB |
| DSNZPxxx: | DSN6SPRM PARAMDEG |
- 0
- Specifies no limit to the maximum degree of parallelism that Db2 chooses based on the cost estimate for the query and the system configuration, in particular the number of processors online. Db2 counts both general purpose and zIIP processors equally, and applies further adjustment to determine the degree to use.
- 1–254
- Specifies the maximum degree of parallelism that Db2 uses.
When optimization hints for parallelism are used, the value of the PARAMDEG subsystem parameter does not limit the degree of parallelism at bind time. However, the value of the PARAMDEG subsystem parameter is enforced at execution time. So, if the value of the PARAMDEG subsystem parameter is lower than the degree of parallelism that is specified at bind time, the degree of parallelism is reduced at execution time.
Tip: For
systems with more than two zIIP
processors configured, use the number of zIIP processors as the starting value, and then
adjust as needed for your response time requirements.