RE: enq: SV - contention on RAC EXADATA

Which bundle patch do you have installed at this point? Are you patching on a regular basis? If your several patches behind, that's the first thing I'd do - get caught up.

Bug 12842402 "enq: SV - contention" using ORDERED Sequences in RAC - supposed to be fixed in 12.1 and was also fixed since the Apr 2013 PSU for 11.2 - unless there is a regression. That never happens.

Are you seeing any other performance issues at all? You might want to run exacheck (or whatever they call it now) and see if anything shows up there.

RF

-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Mladen Gogala Sent: Wednesday, June 15, 2016 12:11 AM
To: oracle-l_at_freelists.org
Subject: Re: enq: SV - contention on RAC EXADATA

Have you tried running SQL trace (10046)? Oracle support search yields the following information:

Bug 12842402 "enq: SV - contention" using ORDERED Sequences in RAC

So, are your sequences ordered? Ordered sequences have been a bane of RAC application since the time immemorial, since Oracle 8i and OPS. Also, do you have any enq HW waits? It's a high water mark wait, a sign that your sequence cache is too small. In any case, I would run 10046 trace on the application. AWR and oracle-l are not sufficient in this case.

Regards

On 6/14/2016 5:14 AM, Pawel Smolarz wrote:
> Hi,
>
> Hi,
>
> On Exadata RAC database 12.1.0.2.0 we have problems with queries:
>
> SELECT schema.sequence_name.NEXTVAL
> FROM DUAL CONNECT BY ROWNUM <= :v1
>
> huge waits on Foreground Events:
> Event Waits Total Wait Time (sec) Wait Avg(ms) % DB time Wait Class DB
> CPU 2.1M 37.5 resmgr:cpu quantum 1.1E+08 1.2M 11.21 21.6 Scheduler
> enq: SV - contention 83,224,234 1.1M 12.91 18.8 Other
>
> I know that is BUG but fix has been included in 12.1.0.1
>
> Anyone has a experience with this type of event?
> A lot of CPU has been consume by these sessions .
>
> Regards,
> Pawel
> --
> http://www.freelists.org/webpage/oracle-l
>
>

--
--
Mladen Gogala
Oracle Consultant
http://mgogala.freehostia.com

DISCLAIMER: I am solely responsible for any opinion expressed in this email

--
http://www.freelists.org/webpage/oracle-l


--
http://www.freelists.org/webpage/oracle-l