Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Mailing Lists -> Oracle-L -> Re: Re: _wait_for_sync , dirty buffer flushing and direct reads in parallel

Re: Re: _wait_for_sync , dirty buffer flushing and direct reads in parallel

From: Anjo Kolk <anjo_at_oraperf.com>
Date: Thu, 20 Nov 2003 08:20:33 -0800
Message-ID: <F001.005D7454.20031120082033@fatcity.com>

The infamous event "log file sync"will basically disapear. So you can see what this does to the system, by looking v$system_event to see how much "log file sync" there is.

Anjo.

> I think my understanding was wrong. _wait_for_sync actually only changes
the
> behavior of foreground processes. When set to false, they don't wait for
LGWR
> to write redo records to disk; instead they continue to do their work as
if log
> file sync already finished. It *does not* change any behavior of LGWR,
> notification or not. Correct me if I'm wrong again.
>
> I'm still interested in Tanel's benchmark, though. Only that is
scientific.
>
> Yong Huang
>
> --- Yong Huang <yong321_at_yahoo.com>, i.e. myself, wrote a few minutes ago:
> > Tanel,
> >
> > Did you observe better performance? By how much? Do please let us know!
> >
> > From what I read, _wait_for_sync when set to false means LGWR
immediately
> > notifies user (foreground) processes that redo record writes are done
(even
> > though they're not). When you say the parameter only affects LGWR, you
need
> > to
> > clarify what you mean by "affect"; it changes the notification (posting)
> > behavior of LGWR therefore changes the behavior of waiting processes
(*when*
> > they stop waiting). Just semantics.
> >
> > Yong Huang
> >
> > --- Tanel Poder <tanel.poder.003_at_mail.ee> wrote:
> > > Anjo,
> > >
> > > I also thought it affects only lgwr sync, but Jonathan Lewis once told
that
> > > it affects any disk writes...
> > >
> > > If it affects only lgwr, then great, I can make Apps upgrades, which
do
> > > really lots of DDLs and small transactions, quite much faster that
way...
> > >
> > > Thank you,
> > > Tanel.
> > >
> > >
> > > > _wait_for_sync basically meant that a session is waiting for the
sync
> > > > of the
> > > > redo by the lgwr. Normally the redo log writer writes to disk and
then
> > > > notifies the session that the transaction is completed. By setting
> > > > this to
> > > > false, you no longer wait for the redo to go to disk.
> > > >
> > > > That has no impact on your situation.
> > > >
> > > > Anjo.
>
>
> __________________________________
> Do you Yahoo!?
> Free Pop-Up Blocker - Get it now
> http://companion.yahoo.com/
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Yong Huang
> INET: yong321_at_yahoo.com
>
> Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> San Diego, California -- Mailing list and web hosting services
> ---------------------------------------------------------------------
> To REMOVE yourself from this mailing list, send an E-Mail message
> to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
> the message BODY, include a line containing: UNSUB ORACLE-L
> (or the name of mailing list you want to be removed from). You may
> also send the HELP command for other information (like subscribing).
>

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Anjo Kolk
  INET: anjo_at_oraperf.com

Fat City Network Services    -- 858-538-5051 http://www.fatcity.com
San Diego, California        -- Mailing list and web hosting services
---------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from).  You may
also send the HELP command for other information (like subscribing).
Received on Thu Nov 20 2003 - 10:20:33 CST

Original text of this message

HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US