Re: Redo log groups

Hi there,
Additional Redolog Members( Mirrors) are required just for additional Protection, so that LGWR continues to write even if any member (Redo Log file) is unavailabe.
You can also Mirror the Redo Log files at the Hardware level only. Having too many Members might slow down the LGWR process as it needs to write to all of them in parallel. I would suggest just 2 or 3 members for a REdo Log Group.

The Number and Size of a Redolog Group should depend on the Transaction volume.This becomes critical if the Database is operated in ARCHIVELOG mode becos it is important for the LGWR process to continue writing to the RedoLog files without having to wait for the ARCH process to complete copying the Filled Online redolog file to the LOG_ARCH_DEST location.

If you encounter any messages like 'cannot allocate log' in the alert.log file then you can increase the number of Redolog files providing more room for LGWR to perform transaction logging and time for ARCH process to complete the Copy.

You can also increase the Size of the Log file if the Log Switches are happening too rapidly. It should be tuned so that approx 2/3 switches happen in any 1 hour time interval.

Hope this note helps..

-Thiru
Joao Ricardo B Oliveira wrote:

> hi there:
>
> Anyone can explain when we need to create more Redo Log members or Redo
> Log groups ?
>
> Another question is :
>
> If i submit several jobs in the OEM, like this :
>
> 1.broadcast message 'Shutdown in 10 minutes'
> 2.shutdown immediate everyday at 18:00
> 3.backup database when database down at 18:10
>
> if one of them fails, for example the shutdown, the backup also
> fails ?
>
> if i want to backup directly to a tape (HP Surestore Dat8) the backup
> manager asks for the Tape Device ID... where can i find it ?
>
> Thankx
>
> jricardo_at_ipb.pt
>
> "Oracle the edge @ side ..." by me...
Received on Tue Jul 20 1999 - 11:27:39 CDT