Controlling system wide parallel processing for queries

 

You can use the QQRYDEGREE system value to control parallel processing for a server. The current value of the system value can be displayed or modified using the following CL commands:

The special values for QQRYDEGREE control whether parallel processing is allowed by default for all jobs on the server. The possible values are:

*NONE

No parallel processing is allowed for database query processing.

*IO

I/O parallel processing is allowed for queries.

*OPTIMIZE

The query optimizer can choose to use any number of tasks for either I/O or SMP parallel processing to process the queries. SMP parallel processing is used only if the DB2® UDB Symmetric Multiprocessing feature is installed. The query optimizer chooses to use parallel processing to minimize elapsed time based on the job's share of the memory in the pool.

*MAX

The query optimizer can choose to use either I/O or SMP parallel processing to process the query. SMP parallel processing can be used only if the DB2 UDB Symmetric Multiprocessing feature is installed. The choices made by the query optimizer are similar to those made for parameter value *OPTIMIZE, except the optimizer assumes that all active memory in the pool can be used to process the query.

The default value of the QQRYDEGREE system value is *NONE, so change the value if you want parallel query processing as the default for jobs run on the server.

Changing this system value affects all jobs that will be run or are currently running on the server whose DEGREE query attribute is *SYSVAL. However, queries that have already been started or queries using reusable ODPs are not affected.

 

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Control parallel processing for queries