Control parallel processing for queries

 

There are two types of parallel processing available. The first is a parallel I/O that is available at no charge. The second is DB2^® UDB Symmetric Multiprocessing, a feature that you can purchase. You can turn parallel processing on and off.

Even though parallelism has been enabled for a server or given job, the individual queries that run in a job might not actually use a parallel method. This might be because of functional restrictions, or the optimizer might choose a non-parallel method because it runs faster.

Because queries being processed with parallel access methods aggressively use main storage, CPU, and disk resources, the number of queries that use parallel processing should be limited and controlled.

• Controlling system wide parallel processing for queries
  You can use the QQRYDEGREE system value to control parallel processing for a server.

• Controlling job level parallel processing for queries
  You can also control query parallel processing at the job level using the DEGREE parameter of the Change Query Attributes (CHGQRYA) command or in the QAQQINI file, or using the SET_CURRENT_DEGREE SQL statement.

 

Parent topic:

Change the attributes of your queries with the Change Query Attributes (CHGQRYA) command