Parallel Query in RAC
by Riyaj Shamsudeen
Parallel Execution (PX) is a powerful feature that makes it possible to utilize numerous processes to process millions, if not billions, of rows. In RAC, multiple nodes can be employed to execute a single SQL statement if the data set processed by a single SQL statement is huge.
In a single-instance database, PX server processes are allocated in the local instance. In a RAC database, PX server processes can be allocated in any or all active instances depending upon the configuration. For example, a PX query initiated in instance 1 can employ PX server processes from instances 1, 2, and 3 (in ...