At runtime, if the number of worker processes specified in the query plan is not available, Adaptive Server creates an adjusted query plan to execute the query using fewer worker processes. This is called a runtime adjustment, and it can result in serial execution of the query.
A runtime adjustment now and then probably indicates an occasional, momentary bottleneck. Frequent runtime adjustments indicate that the system may not be configured with enough worker processes for the workload.
See “Runtime adjustments to worker processes” for more information.
You can also use the set process_limit_action option to control whether a query or stored procedure should silently use an adjusted plan, whether it should warn the user, or whether the command should fail if it cannot use the optimal number of worker processes.
See “Using set process_limit_action” for more information.
Runtime adjustments are transparent to end users, except:
A query that normally runs in parallel may perform very slowly in serial.
If set process_limit_action is in effect, they may get a warning, or the query may be aborted, depending on the setting.