Re: real applicaton cluster

"robson" <dbanewbie_at_yahoo.com.br> wrote in message news:514f866a.0403170543.391d00a2_at_posting.google.com...
> hi, i am brasilian and i know a little inglish.
> i am working with oracle9i RAC (Oracle9i Enterprise Edition Release
> 9.2.0.3.0 - Production) and a don't understand about the recover in
> RAC. what is the best configuration to archived log, i used OCFS. each
> node should have the directory to write archived log or can use a OCFS
> to write all archived log of all nodes in the same local.
> thanks.

A lot of RACs use raw devices as the shared disk. But archived redo logs cannot ever be written to raw devices. Therefore, such RACs cannot share their archives by simply writing them to the shared disk. And that's a problem, since during a media recovery, the recovering instance will need to see all archives produced by all instances. Therefore, when you RAC with raw you have to cheat a little, by getting each instance to write its archives to an NFS mount point, which is then visible to the other instances.

But you are in the happy position of using a Cluster File System, and archived redo logs *can* be written to a CFS. Therefore, you can get each instance to archive its thread of redo onto the one, shared, hard disk array. No NFS stuff is involved, since that disk array will already be physically shared between nodes.

Can all instances write their archives to the same *directory* on the shared disk array? Absolutely: not a problem. *PROVIDED* that one instance's archives don't threaten to over-write those already written there by another instance. For example, with a log_archive_format=arch%s.rdo, you'll have problems. Instance 1's log sequence 7 will merrily over-write instance 2's log sequence 7.

Which is why the log_archive_format parameter should always include the "%t" or "%T" variable as well, with an underscore. In other words, set log_archive_format=arch%s_%t.rdo This way, you'll have log "arch7_1.rdo" and log "arch7_2.rdo" from each of two instances, and there is no danger of over-writing.

I'm not sure if that was exactly what you were asking, but I hope it helps a bit anyway.

Regards
HJR Received on Wed Mar 17 2004 - 08:32:15 CST