DB2 Version 4.1
Query CPU Parallelism

DB2 V3.1 provided IO Parallelism -- that is, the ability to start multiple read engines for a single query against a partitioned tablespace. Testing at Norwest showed a 60% reduction in the elapsed time required to scan a large tablespace having 5 partitions, when IO parallelism was used.

Now, DB2 V4.1 provides CPU parallelism -- that is, the ability to decompose a query into multiple operations that can be executed concurrently by multiple CPUs.



DB2 employs both "horizontal" (or "partitioned") parallelism and "vertical" (or "pipelined") parallelism. DB2 can parallelize: Parallelism is not limited to partitioned tablespaces, although according to IBM partitioned tablespaces show the best performance improvements because data is physically separated and distributed (usually) across many disk devices.

To enable parallelism:


Columns have been added to PLAN_TABLE to indicate, in an EXPLAIN, the type and degree of parallel operations performed. But these may be ignored by DB2 at execution time, depending on resource availability.

In any case, do not use CPU parallelism without first consulting with your DBA.



©Copyright 1996 Chuck Anesi all rights reserved