You can turn parallel processing on and off. If the DB2 UDB Symmetric Multiprocessing feature is installed, then you can also turn symmetric multiprocessing (SMP) on and off.
Even though parallelism has been enabled for a system or given job, the individual queries that run in a job might not actually use a parallel method. This might be because of functional restrictions, or the optimizer might choose a non-parallel method because it runs faster. See the previous sections that describe the performance characteristics and restrictions of each of the parallel access methods.
Because queries being processed with parallel access methods aggressively use main storage, CPU, and disk resources, the number of queries that use parallel processing should be limited and controlled.