RE: log file sync (now EBS, RAC, PARALLEL_MAX_SERVERS)
- From: "Mark W. Farnham" <mwf@xxxxxxxx>
- To: <ora_kclosson@xxxxxxxxx>, <Amir.Hameed@xxxxxxxxx>
- Date: Thu, 23 Aug 2012 15:11:00 -0400
Youch!
If you really can't fit your processing need on a single node, then you
usually need to set up application affinity for EBS to fight less with RAC
architecture. So you probably do not want to allow parallel queries to cross
nodes. (You might I suppose if you have a blackout period to run certain
jobs against nothing else, the archetype being open GL period, but even then
it is not a certainty that will run faster on multiple nodes than on a
single node.)
So unless you've got a really good reason you should configure so that
parallel queries on EBS systems cannot cross node boundaries.
Next, with the concurrent manager being able to schedule jobs so that you
can eat up pretty much all the resources on all the nodes, there is a real
question of overall throughput about whether you want any single job to run
in parallel ever. (Please notice I wrote "real question" and that a real
world load mix and real world demands for some individual job to complete
more quickly may mean allowing it to run in parallel justifies sacrificing
overall throughput. Keeping some broad resource hog out of "prime time" [if
in this increasingly global world you still have a "prime time"] might also
justify running some job in parallel even if the consumer does not need it
in a hurry. This tends to be true of large update batch jobs, so if you can
"de-heat" the undo for when routine queries are heavier you can reduce the
total work required to execute the overall load.)
Good luck.
mwf
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Kevin Closson
Sent: Thursday, August 23, 2012 1:49 PM
To: Amir.Hameed@xxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: log file sync
Now I am working on addressing the "direct path read " event which is coming
from a standard EBS statement that contains 'parallel' clause without any
DOP which ends up invoking 144 parallel processes on three RAC nodes
(PARALLEL_MAX_SERVERS is set to 48 on each RAC node).
... Eeek...taming the beast as it were.
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