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Re: Balancing size of RMAN backup pieces

From: EscVector <Junk_at_webthere.com>
Date: 4 Jan 2007 21:05:07 -0800
Message-ID: <1167973506.708428.187370@s80g2000cwa.googlegroups.com>


Andy Kent wrote:
> How does RMAN allocate datafiles to disk-based backup channels and can
> I control this?
>
> What control do I have over this?
>

None... Get more disk.......

Remember backups are key; It's a one way street otherwise.

You could also shrink your undo prior to running the backup. This is difficult if hot, but not if mount. RMAN includes undo in the backup set, wasted space if clean shutdown.

You are buying a problem that you should not have. I say this every time I see backup/disk issues that fall into the database admin's lap. The ratio storage to outage/downtime cost is well worth the investment in storage just as investing in energy saving lights is more expensive at the onset, but amortizes over time.

I think you can find some answers here (not a link - use doc# to search)
B19306_01/backup.102/b14191/rcmbackp009.htm#sthref687

You have few options, but in this case, failure is an option, somewhat..... Setting maxpiecesize and using "backup not backed up" may be the only options at this point if disk can't be allocated for backups. Example is in doc.

Per documentation:
"When making backups, RMAN divides the total number of files requiring backups by the number of allocated channels to calculate the number of files to place in each backup set. Use the MAXSETSIZE parameter to override this calculation and specify how many files should go in each backup set."

this isn't really true because the # of files in the set is dependent on the file size in some sense. If there were only 2 channels with 2 files, 100gb, 1M, the 100gb file would go to one channel and the 1M file would go to the other. That's not really balanced.....

Read info on MAXSETSIZE. I would not use it. I would simply set MAXPIECE and let the backups fail, move the pieces out, then "backup not backed up" making sure I have backup optimization on.

The real issue is that RMAN is best served directly to tape...Gone direct with one of
these....(http://sunsolve.sun.com/handbook_pub/Systems/L700/L700.html) Received on Thu Jan 04 2007 - 23:05:07 CST

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