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RE: log buffer space

From: Pete Sharman <peter.sharman_at_oracle.com>
Date: Fri, 14 Mar 2003 11:24:23 -0800
Message-ID: <F001.0056AA66.20030314112423@fatcity.com>


Maybe finger stutter. I've never seen it mentioned anywhere except as 1/3.

Pete
"Controlling developers is like herding cats." Kevin Loney, Oracle DBA Handbook
"Oh no, it's not. It's much harder than that!" Bruce Pihlamae, long-term Oracle DBA  

-----Original Message-----
Sent: Friday, March 14, 2003 11:04 AM
To: Multiple recipients of list ORACLE-L

Dennis,

The 1MB condition was in 8i as well, at least in 8.1.7, as I mentioned in my original post.

I was always under impresssion that the flush is triggered by the buffer being 1/3rd full; but KG mentioned it was 2/3rd, not 1/3rd and I was wondering where he got that information from and if it's documented. It true, that will certainly invalidate most of the what the fine manuals and Oracle Support analysts have said.

Any ideas, anybody?

Arup

> Add one more condition:
> New in Oracle 9i, it will write when 1 meg is reached, so the 1/3
> criteria is never reached if you use a big buffer.
>
> Dennis Williams
> DBA, 40%OCP, 100% DBA
> Lifetouch, Inc.
> dwilliams_at_lifetouch.com
>
>
> -----Original Message-----
> Sent: Friday, March 14, 2003 8:59 AM
> To: Multiple recipients of list ORACLE-L
>
>
> KG,
>
> Thanks for the response. Just for my curiosity, is it documented
> somewhere that the log buffer if flushed when 2/3rd full? From the
> Manual /server.920/a96524/c09procs.htm#3158 (please check the URL in
> OTN, the

first
> part is not complete), here is an excerpt
>
> <MANUAL>
> LGWR writes one contiguous portion of the buffer to disk. LGWR writes:
> a.. A commit record when a user process commits a transaction
> b.. Redo log buffers
> a.. Every three seconds
> b.. When the redo log buffer is one-third full
> c.. When a DBWn process writes modified buffers to disk, if
> necessary
>
> </MANUAL>
>
> At least this was the behavior I tested in 8.1.7; although I have not
tested
> in 9i. This has also been stated by several Oracle Support Analysts.
>
> Thanks.
>
> Arup Nanda
>
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> Sent: Friday, March 14, 2003 7:32 AM
>
>
> > Arup:
> >
> > <NO FLAMES>
> > The second condition is not quite true. It is 2/3 full in the
> > current versions. </NO FLAMES>
> >
> > It is very easy to test with the event 10046^8.
> >
> > KG
> >
> >
> > --- Arup Nanda <orarup_at_hotmail.com> wrote:
> > > AK,
> > >
> > > If the log buffer is at least 4MB, then increasing it will not
> > > help, rather it may hurt. The log buffer is flushed when any of
> > > the the follwoing occur
> > > (i) 1 MB is filled up
> > > (2) 1/3rd is filled up
> > > (3) every 3 seconds
> > > (4) when a checkpoint occurs
> > > (5) when a commit occurs.
> > >
> > > Therefore, see if any of these could be the problem. It's easy to
> > > check #s 4 and 3.
> > >
> > > As Kirti suggested, the problem could be due to the redo logs
> > > being on a busy disk, or even a slow one.
> > >
> > > HTH.
> > >
> > > Arup
> > > ----- Original Message -----
> > > From: Deshpande, Kirti
> > > To: Multiple recipients of list ORACLE-L
> > > Sent: Thursday, March 13, 2003 8:13 PM
> > > Subject: RE: log buffer space
> > >
> > >
> > > Increasing log_buffer size is an option, if it is really small.
> > > I would also check if the redo logs are on a busy disk. If so,
> > > try moving those (or other busy data files on the same disk) to
> > > other not-so-busy disks.
> > >
> > > - Kirti
> >
> >
> > =====
> > Have a nice day !!
> > ------------------------------------------------------------
> > Best Regards,
> > K Gopalakrishnan,
> > Bangalore, INDIA.
> > --
> > Please see the official ORACLE-L FAQ: http://www.orafaq.net
> > --
> > Author: K Gopalakrishnan
> > INET: kaygopal_at_yahoo.com
> >
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> --
> Author: Arup Nanda
> INET: orarup_at_hotmail.com
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Arup Nanda
  INET: orarup_at_hotmail.com

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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Pete Sharman
  INET: peter.sharman_at_oracle.com

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Received on Fri Mar 14 2003 - 13:24:23 CST

Original text of this message

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