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RE: rman backup to disk, mismatch in amount backed up to each cha nnel

From: Hitchman, Peter <Peter.Hitchman_at_thomson.com>
Date: Fri, 22 Oct 2004 15:08:05 +0100
Message-ID: <8D697B8FCEBB3744B3A1E4AE15E8331E4B8813@der-lon-msg-03.derwent.co.uk>


Hi,
Thanks for the reply. Apparently we allocate two channels to speed things up, but I don't know enough about the hardware set-up to be sure if the disk I/O is acually separated out. Two of us have been looking into this issue and if we cannot solve it we may well have to go the way you suggest.

Regards

Pete

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Mark W. Farnham Sent: 22 October 2004 14:53
To: oracle-l_at_freelists.org
Subject: RE: rman backup to disk, mismatch in amount backed up to each channel

Unless your disk i/o communications pathways are truly separate, I would actually suggest that you use only one channel and alternate the backup destinations. I might even do this just for the reliability increase, even if it takes a bit longer in the case where you really do have i/o pathways that are non-interfering. Then alternate your channels each backup, which preserves your ability to even out the storage size and means that if one or the other destination fails, you still have an online backup. A belt and suspenders. Now each alternation is going to the receiver about 75% full, so you only have room for two copies. You'd need a little more space if you wanted to cover the unlikely condition that "rman2" blows up (idle though it may be at the time) during a backup to "rman1." You'd need a little more space to have two complete at all times.

Now I did not really answer your question, which certainly would become relevant if someone had, say, "rman1a", "rman2a", "rman1b", and "rman2b" and they wanted to evenly split rman1a and rman1b on "a" days and evenly split rman1b and rman2b on "b" days. Other than declaring the limit on each to be only half the available space, I'm not sure how to do that, and I hope someone more expert than me at rman operations chimes in.

Regards,

mwf



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Received on Fri Oct 22 2004 - 09:05:43 CDT

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