Some Statements Unexpectedly Run in Parallel With Auto DOP (Parallel_Degree_Policy = Auto or Limited) (Doc ID 1643540.1)

Last updated on APRIL 09, 2014

Applies to:

Oracle Database - Enterprise Edition - Version 11.2.0.2 to 12.1.0.1 [Release 11.2 to 12.1]
Information in this document applies to any platform.

Symptoms

With AUTO DOP, some queries that have less elapsed time with serial execution, get executed in parallel.

As an example:

If we generate 10046 trace file for problematic select statement, we can see the below:


Elapsed time is less with serial execution(in second case). So, ideally with AUTO DOP set, it should go for serial execution only.
However, it goes for parallel execution.

Cause

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