RE: Database perfortmance degraded drastically after upgrading the database from Oracle 102.0.4 to Oracle 11.2.0.3
Date: Thu, 22 Oct 2015 10:11:15 +0100
Message-ID: <DUB408-EAS300B0C5AFAB1A3FC00C730EA1270_at_phx.gbl>
Ram,
Not sure there is a solution as such to direct reads because it's deliberate behaviour.
When direct reads are a problem it's often just inefficient execution plan - either a flip to a bad plan or just previous inefficiencies being hidden by the buffer cache?
So if it's a problem then do fewer full segment scans? Tune queries...
Otherwise you can influence the inputs into the adaptive decision - there are quite a few articles out there about this.
E.g
Larger buffer cache
Fiddle with the thresholds
Etc
Regarding changes in 12c, this is not something I've investigated personally. Nor do we have any prod systems on 12c within my scope at work.
Mladen said earlier that he had an impression it was less of an issue.
Maybe?
Big table cache perhaps?
http://progeeking.com/2014/10/03/rac-12c-direct-path-reads/
Hope this helps.
Dom.
Sent from my Windows Phone
From: Ram Raman<mailto:veeeraman_at_gmail.com> Sent: 22/10/2015 03:47
To: dombrooks_at_hotmail.com<mailto:dombrooks_at_hotmail.com> Cc: gogala.mladen_at_gmail.com<mailto:gogala.mladen_at_gmail.com>; ORACLE-L<mailto:oracle-l_at_freelists.org> Subject: Re: Database perfortmance degraded drastically after upgrading the database from Oracle 102.0.4 to Oracle 11.2.0.3
> For direct path reads, it's worth it. It's one of the most common cause of
> problems on this upgrade path.
>
Dominic, do you know the solution to the issue?
does this happen with upgrades to 12 from 10g also?
Thanks.
-- http://www.freelists.org/webpage/oracle-lReceived on Thu Oct 22 2015 - 11:11:15 CEST