There are two types of parallel processing available. The first is a parallel I/O that is available at no charge. The second is DB2® UDB Symmetric Multiprocessing, a feature that you can purchase. You can turn parallel processing on and off.
Even though parallelism has been enabled for a server 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.
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.