Re: Do we need multiple REDOLOG member if it is already on SAN box?

From: Mark D Powell <>
Date: Sat, 30 Apr 2011 06:58:25 -0700 (PDT)
Message-ID: <>

On Apr 29, 3:12 pm, charles <> wrote:
> > This is not exactly a new type question.  Various people will have
> > different answers here.
> > On most of my dev/test databases ... no I don't use it multiple
> > members in a redolog group usually.
> > Production databases I will go case by case.  Highly critical systems
> > sure why not.
> > Have I ever lost a redolog group or just one member of a group?  Not
> > so far ...
> Here is our SA's comment
> I'm NOT fine with this but please remember that I HIGHLY recommend
> against this.  It is a best practice to never do software raid which
> is what you are basically doing. This is very old practice when you
> don't have the infrastructure that we have.

Tell your SA that the Raid-10 will protect the online redo log from disk media failure but it will not protect the log file from logical corruption which is the point of having multiple online redo log members in a redo log group. If you check your DBA Administration manual I believe you will find Oracle recommeds having mirrowing the online redo logs at the Oracle level, that is, two or more redo log file members per group.

Can you live with only one, yes. The odds are in your favor that you will never have an outage due to corruption of the logs, but if you have multiple redo log members the odds are even better. I would make the decision based on available disk space and performance impact.

HTH -- Mark D Powell -- Received on Sat Apr 30 2011 - 08:58:25 CDT

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