Re: Problem wih Oracle reads from the redo logs.

Thanks for the response,
 The question I have is why is striping redo logs not a good idea, The understanding I have is that disk striping using a volume manager is good no matter what type of wites, the reasoning being that if say the log buffer were to flush out 150M of data, this request would go to the volume manager. the volume manager seeing that the disks are striped, sends out the data to the disks in parallell according to the stripe width and each disk would still be doing a sequential write, even if the controller is the same for those disks, it is still advantageous because the controller delay is a lot less than disk delays.

Vitaliy Mogilevskiy wrote:

> Ravi Kommalapati wrote:
>
> > Hello,
> > We have created a volume for redo logs by striping across 6 disks
> > using the Veritas volume manger, and we have 4 redo log files 250M each,
> > there are no other files on this volume other than the redo logs.
> > Currently the redo logs switch every 7 minutes during peak usage.
>
> ===> Striping REDO LOGS is not a good idea since LGWR writes sequencially
>
> ** Tuning Redo Log Buffer **
> - to see when check points occure set INIT.ORA you'll get it in the ALERT FILE
> !!!
> LOG_CHECKPOINTS_TO_ALERT=TRUE
>
> - to turn EXTRA checkpoints OFF set:
> LOG_CHECKPOINT_INTERVAL=<LARGEST LOG SIZE>
> LOG_CHECKPOINT_TIMEOUT=FALSE
>
> Run this select statement:
>
> select (req.value*5000)/entries.value "Ratio"
> from v$sysstat req
> , v$sysstat entries
> where req.name = 'redo log space requests'
> and entries.name = 'redo entries'
>
> =========> "Ratio" should be < 1 !!!!!!!!!
>
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> | Vitaliy Mogilevskiy
> | Senior Consultant
> | CORE Technology Group, Inc.
> | E-mail: vit100gain_at_earthlink.net
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Received on Wed Apr 14 1999 - 09:50:53 CDT