Query parallelism problem diagnosis

Query parallelism is the ability to process read-only queries in parallel. Queries that are most likely to be processed in parallel have access paths that perform sequential prefetch against page sets that consist of multiple data sets.

Db2 uses query CP parallelism. A single Db2 subsystem on an z/OS® system with multiple processors uses multiple parallel tasks to process a query.

Db2 uses multiple modes of query parallelism:

DB2 uses multiple modes of query parallelism:

Query I/O parallelism

Db2 prefetches data from several partitions of a table space at one time. A single processor processes the first request from each partition, then the second request from each partition, and so on. The processor does not wait for I/O, but there is only one processing task.

Query CP parallelism

A single Db2 subsystem on an z/OS system with multiple processors uses multiple parallel tasks to process a query.