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Message Posted: Thu, 25 Oct 2001 @ 15:05:05 GMT

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Subj:   Re: BAR Poll
From:   Paul Johnson

We use Veritas Netbackup across all platforms, including the NCR 5250. There is a single SCSI drive attached to one of the four nodes. This is supplied with data at it's peak throughput of 70GB/hr. The DBMS is therefore not the limiting factor, as usual it's the tape drive.

On an MVS system the 3480 style tape drives tend to run much slower than this at maybe 5GB/hr to a single drive.

Cluster based backups can be used successfully so long as there are enough tape drives available to export more than one cluster at a time. This is the only way to overcome the limitation of the tape drive throughput.

In the past I have run four MVS cluster-based backups concurrently, each backing up 3 amps (1 cluster) of the same large table (5 billion rows, or about 100 million/amp). Running four lots of four jobs brought the elapse time down from about 2 days to a few hours.

It pays to try a different number of sessions/amp and which amps (i.e. clusters) to backup concurrently to spread the workload. I think we settled on 2 or 3 sessions/amp in the end.

Paul Johnson.

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