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RE: Lots and lots of redo logs

From: Bill Buchan <>
Date: Fri, 14 Sep 2001 09:26:44 -0700
Message-ID: <>

!! Please do not post Off Topic to this List !!

How big a performance issue is the location of the log file on disk? Even if I create the minimum of 2 archive log groups, how can I be sure the controller hasn't put these on the outer platters anyway? Since these are log files then the writes will be sequential anyway (does that make a difference?) - showing my hardware ignorance here!

As you said:

"But in my opinion here is my priorities. 1. Recoverability
2. Performance"

I would have thought that having lots of archive log groups (normally) not overwritten for a few days in addition to properly archived logs would boost my recoverability with negligible impact on performance. (Incidentally the MAXLOGFILES maximum value is 255, on Linux anyway).

- Bill.

At 07:10 14/09/01 -0800, you wrote:
>!! Please do not post Off Topic to this List !!
>It is very common for people to see all that free space and want to fill it.
>Avoid the desire, fill it with a blank file. Disks are cheap and if you
>store things on the outer platters performance will suffer.
>Redo logs and other things in oracle waste disk space as drives get bigger,
>it is unavoidable. But using the space for something totally defeats the
>purpose of good configurations.
>"Do not criticize someone until you walked a mile in their shoes, that way
>when you criticize them, you are a mile a way and have their shoes."
>Christopher R. Spence
>Oracle DBA
>Phone: (978) 322-5744
>Fax: (707) 885-2275
>73 Princeton Street
>North, Chelmsford 01863
>-----Original Message-----
>Sent: Friday, September 14, 2001 10:35 AM
>To: Multiple recipients of list ORACLE-L
>!! Please do not post Off Topic to this List !!
>Thanks. That's a very good point. I agree that ARCHIVELOG mode will be
>However, I still have this big disk just for redo logs, so I'm tempted to
>fill it anyway. This will be a "sort of" supplementary backup in case the
>archive disk (+ database disks) crash before the backup. Of course it is
>only "sort of" because, as you say, a runaway process will cycle the logs
>if it generates lots of redo.
>However, this seems better use of the disk space than just having a few log
>groups and leaving the rest of the array empty and unused.
>Unless there are any other implications?
>- Bill.
> >Hi
> >
> >
> >Yes you can untill the day that you have this runaway process that creates
> >20Gb of redo and than crashes your database 5 minutes before the daily
> >offline backup should kick in.
> >
> >But you are only mirroring, why not put your database in archivelogmode.
> >You do not have so much redo per day that your disks/archiver can't handle
> >it. Now if your archive directory is full oracle won't crash, but just stop
> >untill you free up some space (I believe this is the behaviour anyway).
> >
> >
> >
> >Jack

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Author: Bill Buchan

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Received on Fri Sep 14 2001 - 11:26:44 CDT

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