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RE: RMAN Peformance and how to optimise

From: John Kanagaraj <>
Date: Tue, 17 Feb 2004 12:12:36 -0800
Message-ID: <>


If the number of tape and RMAN channels were equal to the number of drives available, then you will have optimized tape streaming during backup (saves backup time) as well as restore time. Increasing the number of channels will not solve, but only degrade your backup (and restore) timings. Why don't you look at disk pooling or staging (I know that is available in ADSM now Tivoli, maybe it is available on Legato 7?) We had a similar issue (with just normal files) 4 - 5 years back and I am speaking with that in mind... (so YMMV)!

John Kanagaraj <><
DB Soft Inc
Phone: 408-970-7002 (W)

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>-----Original Message-----
>[] On Behalf Of
>Sent: Tuesday, February 17, 2004 11:43 AM
>Subject: RMAN Peformance and how to optimise
>We are seeing poor performance when recovering a full database (65 =
>datafiles) , during backup revovery (testing I hasten to add
>so not job =
>or life threatening)
>Oracle 9202 Legato Networker 7 (I think) filesperset 1 2 tape
>drives 8 =
>What appears to be the problem is that the order that the backup was =
>taken (full) does not co-incide with the order that the files
>are being =
>recovered (using RMAN logs to tell the order)
>From NW we are seeing 1 channel reading from tape and laying down the =
>file to disk and 7 channels idle.
>We suspect that they are waiting on the same tape but for a different =
>part of the tape.
>Ideally what we want is a means of RMAN recovering the
>datafiles in the =
>order they are on the tape.
>I have seen a note on Metalink suggesting that either 1 or 2
>channels is =
>best per available tape drive.
>We have to strike a balance betweeen the backup time and the recovery =
>time with neither taking extremes.
>Has anybody done any work in this area that could offer some useful =
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Received on Tue Feb 17 2004 - 14:12:36 CST

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