Re: high average wait time of wait event "virtual circuit wait”

From: du shenglin <shenglin.du_at_gmail.com>
Date: Fri, 16 Nov 2012 20:59:41 +0800
Message-ID: <CAGpGbogn56ix3DCi7B0jNFmeP_bzBCvOhWW=pkYR_p-bQ3MD_w_at_mail.gmail.com>



Great blog, Igor Usoltsev.
Unfortunately, I didn't do the SQL trace at that time. We did failover that database again and after that, the average wait time is back to normal. My query is reading LOB, so each row fetching will need at least one round trip. The question for me is that what caused the increasing of 'average wait time' for the event virtual circuit wait.

Thanks
Shenglin

On Fri, Nov 16, 2012 at 7:00 PM, <igorus_at_yandex-team.ru> wrote:

> Hello Shenglin,
>
> Look at SQL Trace, and may be this similar problem description helps you -
> http://igorusoltsev.wordpress.com/2011/03/26/virtual-circuit-wait/ - low
> arraysize and huge virtual circuit wait
>
> Regards, Igor Usoltsev
>
> 15.11.2012, 20:38, "du shenglin" <shenglin.du_at_gmail.com>:
> > Hi all,
> > I saw high average wait time of wait event "virtual circuit wait” in
> my
> > database.
> >
> > host: solaris sparc 64bit
> > database version: 11g Enterprise Edition Release 11.2.0.2.0 - 64bit
> > Production
> > the database is MTS mode, with 60 dispatcher and 300 shared server.
> Only
> > less than 10 busy dispatcher and less than 200 active shared server
> during
> > high wait for "virtual circuit wait”.
> >
> > I started to see the high wait event of "virtual circuit wait” after
> > failover to a new node. Sometimes, the average wait time of "virtual
> > circuit wait” was over 25 ms. Normally, it is only about 1ms.
> >
> > I saw the high wait of this event with P2=3. Per oracle document, the
> > event '"virtual circuit wait” mean the shared server is blocked waiting
> on
> > a specific circuit or message, the P2=3 means waiting on a send to the
> > client. Checking the related SQL, most of them were reading some LOB
> > columns.
> >
> > I suspected it was related to network issue. however, there is no high
> > wait event and high average wait time of 'sql net more data to client'.
> >
> > Do you know what may cause the high average wait time of "virtual
> > circuit wait”? Any comments are welcomed.
> >
> > Thanks
> > Shenglin
> >
> > --
> > http://www.freelists.org/webpage/oracle-l
>

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Received on Fri Nov 16 2012 - 13:59:41 CET

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