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Home -> Community -> Mailing Lists -> Oracle-L -> Re: RMAN Peformance and how to optimise
Hi John, the first thing that I would look at is whether the Legato
"sessions" setting is set to 1. You've done the right thing with
"filesperset" in RMAN, but if sessions is greater than 1 then Legato will
interleave multiple RMAN channels onto a single tape. I've had good luck
with getting maximum restore performance with one channel per drive,
filesperset = 1 (RMAN), and sessions = 1 (Legato). Obviously the idea is to
read as little tape as possible to restore the data you need. If that still
isn't fast enough then John K's idea to stage to disk first is a good approach.
Andy Rivenes
arivenes_at_llnl.gov
At 07:42 PM 2/17/2004 +0000, you wrote:
>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 =
>channels
>
>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 =
>insights
>
>Thanks
>
>
>John
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