Using parallelism

DB2 can use more than one processor to access the database, allowing parallel execution of complex SQL requests to be divided among the processors within a single database partition.

Getting ready

Allow for downtime to restart the instance when setting DBM configuration.

How to do it...

1. Set a registry for parallel I/O.

2. For RAID 5 configuration, set this registry variable and see the discussion later on in this section:

   	[db2instp@nodedb21 ~]$ db2set DB2_PARALLEL_IO=*
   

3. Get the current configuration for intra partition parallelism. In this case, intra-partition parallelism was not set:

   [db2inst1@nodedb21 tmp]$ db2 get dbm cfg | grep -E  "INTRA_PARALLEL|MAX_QUERYDEGREE"
    Maximum query degree of parallelism   (MAX_QUERYDEGREE) = ANY
    Enable intra-partition parallelism     (INTRA_PARALLEL) = NO
   

4. Update the current configuration:

   [db2inst1@nodedb21 tmp]$ db2 update dbm cfg using INTRA_PARALLEL YES MAX_QUERYDEGREE -1
   DB20000I  The UPDATE DATABASE MANAGER CONFIGURATION command completed...