Re: RAC PARALLEL

From: Sanjay Mishra <smishra_97_at_yahoo.com>
Date: Fri, 14 Oct 2011 08:46:19 -0700 (PDT)
Message-ID: <1318607179.93756.YahooMailNeo_at_web161203.mail.bf1.yahoo.com>

Changing parallel_force_local to True has brought back the SQL to same and even better performance level. Thanks to all for the help and suggestions. Will be doing more regression testing to make sure if this is the only issue.  
Sanjay

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From: Andrew Kerber <andrew.kerber_at_gmail.com> To: mwf_at_rsiz.com
Cc: tim_at_evdbt.com; Sanjay Mishra <smishra_97_at_yahoo.com>; oracle-l_at_freelists.org Sent: Thursday, October 13, 2011 8:41 AM Subject: Re: RAC PARALLEL

I'm surprised no one mentioned this.  If this is 11g there is a parameter called parallel_force_local.  Make sure this is set to true.  If not, you can end up running parallel operations on remote nodes, which will both adversely affect operations on other nodes, but will also cause massive gc waits when data is returned unless you have a very high speed interconnect (ie, at least 10 gigabit).  On 10g this is done by setting the parallel groups and such, I would have to look it up to find the exact details. 

As others have mentioned, it is unlikely that parallel is a good idea on OLTP, but but some of the other parameters you need to look at are parallel_min_servers, parallel_max_servers.  I have found that setting the parallel_min_servers saves a lot of time in the startup of parallel queries and parallel_max_servers will help keep the load down at high usage times.

(note: resent because I overquoted a few minutes ago).

-- 
Andrew W. Kerber

'If at first you dont succeed, dont take up skydiving.'
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Received on Fri Oct 14 2011 - 10:46:19 CDT