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Re: RMAN Performance Maladies

From: Naqi Mirza <>
Date: Mon, 12 Feb 2007 12:08:17 -0800 (PST)
Message-ID: <>

I just realised - you also mention a drop in performance, have you had a look at the rman rate parameter. Changing this from the default would result in your backups taking longer but could also reduce the load rman places on its reads to your datafiles. Basically it will control the amount of disk bandwidth consumed by rman.

----- Original Message ----
From: Michael Fontana <>
Sent: Monday, 12 February, 2007 9:15:22 PM
Subject: RMAN Performance Maladies

We have just implemented RMAN against our largest Siebel implementation
(don't laugh - but it's less then 1/2 terrabyte).
We did so because now that we have upgraded to Oracle 10gR2 (
we can take advantage of flash recovery features and full backup
compression similar to which we achived with our old backup product (BMC
Sqlbacktrack).  We customarily take full backups nightly, as per our
SLA, and at this point, incrementals are not an option.  However, the
actual runtime to complete a full database backup with RMAN compared to
SqlBackTrack has gone from 30 minutes to over 4 1/2 hours!  

I have seen anecdotal reports of long runtimes for full RMAN backups on
this list, but I've seen an overwhelming number of guffaws from the more
elite and experienced poster indicating that this must be user error or
some other database performance problem that any competent DBA should
easily be able to solve without posting to this list.  However, even
after opening an SR with Oracle support, who seems to believe our
runtime is in the expected range, we still believe something can be done
to overcome the huge IO spike and slow performance we are witnessing
during the backup, and we are not that experienced with RMAN from a
performance and tuning perspective, and would appreciated anyone's
insights or experiences.

My question is - has anyone actually run RMAN against a large (> 200g)
database right out of the box without tuning?  

Has anyone spent a great deal of time tuning?

We are running 4 channels, have an 8 cpu Sunsparc solaris with 16g of
memory, and have experimented with recommended parameter settings for
maxsetsize and maxfilesperset without success.  Any information or
assistance or comment would be appreciated, thanks in advance!


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Received on Mon Feb 12 2007 - 14:08:17 CST

Original text of this message