Some Statements Unexpectedly Run in Parallel With Auto DOP (Parallel_Degree_Policy = Auto or Limited)
(Doc ID 1643540.1)
Last updated on MARCH 10, 2020
Applies to:Oracle Database - Enterprise Edition - Version 18.104.22.168 to 22.214.171.124 [Release 11.2 to 12.1]
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Information in this document applies to any platform.
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.
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