When Parallel Doesn't Happen

From: Kellyn Pedersen <kjped1313_at_yahoo.com>
Date: Thu, 1 Oct 2009 09:45:38 -0700 (PDT)
Message-ID: <35396.35827.qm_at_web32006.mail.mud.yahoo.com>

I have just started for a company that applies to the philosophy of too much of a good thing is really a good thing, so bear with me...

The code has parallel hints everywhere- degrees often set to 8 in multiple hints in one DML or DDL set, (parallel_threads_per_cpu=2, so start doing the math...)  The parallel_server is set  anywhere from 96 to 168 and someone had the idea that as long as they set the threshold high enough, everything would run. 

I have never seen parallel used the way it is here and I've come across some very interesting challenges.  The amount of slaves being allocated to a process are being downgraded as resources are becoming limited by the poor choices made in some of these simultaneous requests.
queries parallelized                              10443
DDL statements parallelized                    106
DFO trees parallelized                     10549
Parallel operations not downgraded   10457 Parallel operations downgraded to serial 19
Parallel operations downgraded 75 to 99 pct 0
Parallel operations downgraded 50 to 75 pct 0
Parallel operations downgraded 25 to 50 pct 92
Parallel operations downgraded 1 to 25 pct 0 PX local messages sent 205011362
PX local messages recv'd 230002397
PX remote messages sent 0
PX remote messages recv'd 0
Received on Thu Oct 01 2009 - 11:45:38 CDT

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