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Re: Backup of large databases

From: Peter J. Holzer <>
Date: Sun, 28 Oct 2007 14:37:36 +0100
Message-ID: <>

On 2007-10-26 20:53, <> wrote:
> I am still on Oracle on HP UNIX 11, I am using RMAN for
> backups. We are going to setup a large data warehouse which is
> expected to grow to 500GB. My main concerns is backup times taken by
> database backups. Currently, for 20GB database size, full backups take
> 12 hours to complete, I am using RMAN with default parameters and only
> one channel is being used:
> Allocate channel ch1 type 'SBT_TAPE';
> I think reason backups take so long is Network band width. Our servers
> reside in a local data center but backups are done over WAN in central
> data center where all Netbackup tape servers and tape drives reside.
> We cannot move our databases to central data center.

20 GB in 12 hours translates roughly to 4 Mbits/s. Does that sound right?

> Only parameters which I know to experiment are usng multiple channels
> and tuning some init.ora parameters documented in RMAN manual.

If the network is the bottleneck, no amount of tweaking will make a full backup faster. Invest in a faster line, or make the backups locally and ship the tapes to the central location if you want to store them off-site.

If you know that the changes in an acceptable timeframe (maybe an hour or a day) will always be less than the available bandwidth, you can use some incremental scheme (e.g., continously sending the archive logs, or replicating the whole DB). But this won't work if you need to do some large reorganizations.


   _  | Peter J. Holzer    | It took a genius to create [TeX],
|_|_) | Sysadmin WSR       | and it takes a genius to maintain it.
| |   |         | That's not engineering, that's art.
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Received on Sun Oct 28 2007 - 08:37:36 CDT

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