RE: Odd Parallelism Behavior (11.2.0.4) when DEGREE=DEFAULT and INSTANCES=DEFAULT
Date: Tue, 15 Mar 2016 19:38:17 +0000
Message-ID: <A66A222B7625DC479778336ACBC73A1F1E19BFA9_at_NASHC736PN1.UBSPROD.MSAD.UBS.NET>
Adding some stuff that I had read through for some earlier issue Hope it helps
https://www.pythian.com/blog/secrets-of-oracles-automatic-degree-of-parallelism/
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Rich J
Sent: Tuesday, March 15, 2016 3:16 PM
To: oracle-l_at_freelists.org
Subject: Re: Odd Parallelism Behavior (11.2.0.4) when DEGREE=DEFAULT and INSTANCES=DEFAULT
On 2016/03/15 13:05, Chris Taylor wrote:
"How to determine the Oracle default degree of parallelism - what controls/influences the "default" degree?"
I thought it was default=1 but obviously that isn't true. Is there some way I can find the calculated DEFAULT degree of parallelism that Oracle might be using ?
I think http://docs.oracle.com/cd/E11882_01/server.112/e41084/clauses006.htm#SQLRF20024 holds the answer:
"If PARALLEL_DEGREE_POLICY is set to MANUAL, then the optimizer calculates a degree of parallelism equal to the number of CPUs available on all participating instances times the value of the PARALLEL_THREADS_PER_CPU initialization parameter."
The other scenarios are found on that page as well.
HTH! GL! Rich
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