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
you must 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.
