Query Parallelism
In order to reduce elapsed time for a query, DB2 can provide a query with parallel resources, such as several I/O paths or processors. By taking advantage of these resources, queries can run in a shorter period of time, allowing more work to be pushed through the system. Parallelism can help improve the performance of I/O and CPU bound read-only queries. It can help queries that are reading large amounts of data, regardless of the filtration.
There is some overhead associated with the use of parallelism in terms of CPU. DB2 scales processor-intensive work across all available processors. Parallelism can average less than 1 percent additional CPU overhead for long-running queries and less than 10 percent for short-running queries. ...
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