RE: log buffer size and log file syncs

From: coskan gundogar <coskan_at_gmail.com>
Date: Wed, 2 May 2012 08:07:23 +0100
Message-ID: <CAGLGTvOm41uCD2mreGY6wqyqOu9MdzzoQ7-mikXGiByidZzhfw_at_mail.gmail.com>



I think if you are not able to run snapper which is plsql block and does not need any installation that change management better be revised since it is nothing different than polling v$ tables every second individually Sent from my mobile device
On May 1, 2012 7:11 PM, "CRISLER, JON A" <JC1706_at_att.com> wrote:

> Unfortunately our change control policies prevent me from running Snapper
> on the problem system.
> From: tanel_at_poderc.com [mailto:tanel_at_poderc.com] On Behalf Of Tanel Poder
> Sent: Tuesday, May 01, 2012 11:54 AM
> To: CRISLER, JON A
> Cc: oracle-l
> Subject: Re: log buffer size and log file syncs
>
> Hi Jon,
>
> Increasing LGWR priority would only help if it was currently starving for
> CPU / or waiting too long in the CPU runqueue... Unfortunately on Linux
> there's no easy way to measure this directly. If your load is low (let's
> say only 10 on a 32 CPU machine) then I'd expect that LGWR priority change
> isn't going to help much.
>
> However, I don't like to fix a problem first and then see whether the
> problem existed in first place (trial and error), that's why I asked for
> extra information / hard evidence in form of LGWR's snapper output ...
>
> Tanel.
> On Tue, May 1, 2012 at 6:19 PM, CRISLER, JON A <JC1706_at_att.com<mailto:
> JC1706_at_att.com>> wrote:
> Red Hat Linux 5. We have async DG running but Real Time apply is also
> configured, and redo logs are mirrored. I believe LGWR is not starved for
> CPU given the overall conditions for the system, but I am finding some info
> that putting lgwr in a real-time OS priority would be a good thing.
>
> The default for _high_priority_processes is LMS*|VKTM but I have seen
> some Metalink notes about adding LGWR. I also saw a blog post that
> mentioned you discussed setting this parameter at a HOTSOS seminar, and
> this is something we are considering. Given all the CPU power in this
> server, and all the LMS processes, I don't this would pose a problem.
>
> alter system set "_high_priority_processes"='LMS*|VKTM|LGWR' scope=spfile
> sid='*';
>
>
> From: tanel_at_poderc.com<mailto:tanel_at_poderc.com> [mailto:tanel_at_poderc.com
> <mailto:tanel_at_poderc.com>] On Behalf Of Tanel Poder
> Sent: Monday, April 30, 2012 6:21 PM
>
> To: CRISLER, JON A
> Cc: oracle-l
> Subject: Re: log buffer size and log file syncs
>
> Which OS are you on? If it happens to be Solaris, then prstat -mLp PID
> would show the scheduling latency for LGWR. This would help to find out
> whether LGWR is CPU starved or not.... what load averages do you have?
>
> Also, what does snapper say when ran on LGWR? If you have synchronous DG
> for example, then LGWR would wait for the LNS ack too in addition to the
> log file parallel write wait, before returning OK back to the committing
> session ...
>
> Tanel.
> On Mon, Apr 30, 2012 at 5:56 PM, CRISLER, JON A <JC1706_at_att.com<mailto:
> JC1706_at_att.com>> wrote:
> Interesting thoughts Tanel: in this case of this specific app, the
> majority of the work is made of up small commits to a handful of tables on
> a 6 node RAC cluster. I/O times are generally quite good, and with 32
> cores per node the CPU and load average is very low. Its 11gR1 - I was
> wondering if some of the tweaks to put LGWR at "real time" priority that
> are mentioned for 10g also apply to 11g.
>
>
>
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

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Received on Wed May 02 2012 - 02:07:23 CDT

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