RE: Log file synch / direct path writes

Ramon, along the lines of Beth's idea here, how large are the archive logs you are producing?

Dennis Williams
DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com

-----Original Message-----
Sent: Monday, June 24, 2002 1:19 PM
To: Multiple recipients of list ORACLE-L

Ramon,

For one thing, LGWR will write the log buffer when it is 1/3 full, or if it reaches 1MB. So, its useless to have the log buffer more than 3MB. The space beyond 3MB could never possibly be used.

My .02

Beth

-----Original Message-----
Sent: Monday, June 24, 2002 1:28 PM
To: Multiple recipients of list ORACLE-L

Jared,

Just to clear my thoughts, doubts and keep learning from the list.

What implications can cause having a big log buffer.

As I can remember, LGWR copy data from the log buffer to the redo logs when
log buffer is 1/3 full, timeout, commit and a few more.

So it will fire when the first one occurs, base on that theory, what matters
if the log buffer is 1mb, 10mb, 100mb. Anyway LGWR will copy the data to
the redo logs.

I had some problems of performance the last week and some of you got surprised because I had a log buffer of 100MB.

I have never read some documentation, obviously have to read more and I am
doing it believe me, that tells not to do it.

I would like some comentaries or your considerations about this,

TIA Ramon

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Saturday, June 22, 2002 1:33 PM

>
> Just how large is your overly large log buffer?
>
> 10 meg?
>
> 100 meg?
>
> 1 Gig??? ( ok, I've never heard of one this big,
> but you never know ;)
>
> Jared
>
> On Friday 21 June 2002 12:48, Erik Williams wrote:
> > I have an instance that is waiting on log file synchs. I suspect
that
the
> > waits are a result of a overly large redo log buffer. There are also
> > considerable waits on direct path writes. The redo logs are on
QuickIO,
so
> > I assume that the writes LGWR is writing asynchronously and not a
source
of
> > the log file synchs. I want to be sure that the log file synchs and
direct
> > path writes are not related before I begin to experiment with the
size
of
> > the redo log buffer. How can I be sure that the waits are being
caused
by
> > DBWR and not LGWR? What are possible fixes for the direct path
writes if
it
> > is the DBWR causing them? Multiple DBWR? The datafiles are not on
QuickIO,
> > just the redo.
> >
> > Thanks
> > Erik
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Jared Still
> INET: jkstill_at_cybcon.com
>
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Author: Ramon E. Estevez
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Author: Seefelt, Beth
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Author: DENNIS WILLIAMS
  INET: DWILLIAMS_at_LIFETOUCH.COM

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