Showing posts with label Parallel Processing. Show all posts
Showing posts with label Parallel Processing. Show all posts

Wednesday, February 11, 2015

Parallel Refresh of a Materialized View

This is a quick post regarding materialized views refresh.

Refresh is invoked with a call to procedure DBMS_MVIEW.REFRESH. For large MVs it is highly desired that the refresh takes place in parallel. The REFRESH procedure parameter "parallelism" makes you think that this is the right tool for this job. Nope!

As much attractive as it might seen, this parameter does not help towards the parallelism of the refresh. You have to either include a parallel hint in the SELECT part of the definition statement of the MV (create materialized view) or/and include a PARALLEL DEGREE > 1 to the base tables of the MV.

Thursday, April 11, 2013

parallel hint with no degree specified

In this post we try to investigate what degree of parallelism (DOP) Oracle assigns to DML operations when a parallel hint is used.