You must enable parallel processing for queries when you submit them or when you code your applications. The optimizer does not automatically use parallelism as the chosen access method.
You can use the system-value QQRYDEGREE, the query options file, or the DEGREE parameter on the Change Query Attributes (CHGQRYA) command to control the degree of parallelism that the query optimizer uses. See "Control parallel processing for queries" for information on how to control parallel processing.
A set of database system tasks is created at system startup for use by the database manager. The database manager uses the tasks to process and retrieve data from different disk devices. Since these tasks can be run on multiple processors simultaneously, the elapsed time of a query can be reduced. Even though much of the I/O and CPU processing of a parallel query is done by the tasks, the accounting of the I/O and CPU resources used are transferred to the application job. The summarized I/O and CPU resources for this type of application continue to be accurately displayed by the Work with Active Jobs (WRKACTJOB) command.