Re: Multi-threaded LGWR

From: Mladen Gogala <gogala.mladen_at_gmail.com>
Date: Wed, 27 Apr 2016 05:52:18 -0400
Message-ID: <57208BD2.5080207_at_gmail.com>

Hi Ram,
You are manager, doing POC, running 12c RAC on SuSE? I believe that we have met in Pasadena, CA, have we not? In case I haven't mistaken you for somebody else, please convey my regards to all the nice people at ADP. Regards

On 4/26/2016 6:25 PM, Ram Cheruvattath wrote:
> I am interested in knowing more about this too. We have a 12c RAC
> database with very high volume of redo generation. Recently on a SR
> opened with Oracle support, the recommendation was to turn off log
> writer workers by setting the parameter you mentioned below. We were
> hesitant to do so, as we did not seem to encounter the bugs, which if
> I recall correctly was on AIX and we are on SUSE Linux. We typically
> see around 2 of the 10 workers on our system busy. Others are almost
> always idle.
> Ram
>
> *From:* Mladen Gogala <mailto:gogala.mladen_at_gmail.com>
> *Sent:* Tuesday, April 26, 2016 5:10 PM
> *To:* oracle-l <mailto:oracle-l_at_freelists.org>
> *Subject:* Multi-threaded LGWR
>
> Oracle 12c introduced a new feature, namely multi-threaded LGWR. Of
> course, as it usually happens, you only find out about the new feature
> when it doesn't work. The problems I encountered are documented in the
> following support documents:
>
> * 1957710.1
> * 21915719.8
>
> I was unable to find any controlling parameter in the documentation,
> short of "_use_single_log_writer" which is not really what I want.
> Does anyone have any details on that mechanism? How big must
> LOG_BUFFER be to start an additional thread? How do threads write? My
> guess is that they split the file into peaces and that each thread
> writes into its own peace of file. Obviously, there are some issues.
> In 11G, we saw private redo strands, now we have multi-threaded log
> writer. Did anyone do any research on that? This is a job for
> systemtap, but I have been traveling and didn't have much time.
> Regards
>
> --
> --
> Mladen Gogala
> Oracle Consultant
> http://mgogala.freehostia.com
>
> DISCLAIMER: I am solely responsible for any opinion expressed in this email

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

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


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Received on Wed Apr 27 2016 - 11:52:18 CEST