RE: cloning a terabyte database

On Thu, 2007-12-20 at 14:26 -0500, Mark W. Farnham wrote:
> Second, you wrote “damanged.” Now if many of the files are okay,
> remember that Oracle supports heterochronous recovery just fine, so
> you can just send new copies of the damaged files as long as you have
> the redo logs available back through the oldest file from “test” that
> you want to recover.

When:

• bandwidth is limited
• the data is not too volatile
• (much of) the old database is still available
• the time between the last 'refresh' and this one isn't too long

(all variables that have to be determined on site and judged regarding their net effect)
the I've used rsync as an alternative to copy/restore/reinstantiate with quite some success.
I've experienced cloning operations to e.g. an e=invalidated standby database where the 'speedup factor' reported by rsync was 2000 - 3000!

rsync will, when used with the proper options (see below) compare files at both ends block by block. This is done by checksumming the blocks. Local processes at both ends will do this. Then the checksums are send from the recipient to the sender, and copmared. Only changed bloccks will be transferred.

This will result in a byte-identical copy at the receiving end, just as good old vanilla hot backup would yield. So, if you put a tablespace in backup mode, and use the rsync command to 'copy' its datafiles, rsync will speed up your backup operation significantly if much of the data is there already. It doesn't matter whether the datafiles have been used for testing, or only some of them were destroyed. All unchanged data will remain uncopied, saving precious bandwidth. The rest will be overwritted, filled in, whatever is needed.

For a local network this yields increased copy rates very rarely, just because simply copying the data through a 100Mb or 1Gb LAN is faster than reading all data at both ends, transfer the checksums and compare them.

The rsync command I use (for a database blocksize of 8k) is:

rsync -vcptSz --block-size=8192

Look the rsync man pages of your OS for local flavours of the optionlist.

Best regards,

Carel-Jan Engel

===
If you think education is expensive, try ignorance. (Derek Bok) ===

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> Regards,
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> mwf
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> ______________________________________________________________________
>
> From: oracle-l-bounce_at_freelists.org
> [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Sanjay Mishra
> Sent: Thursday, December 20, 2007 10:03 AM
> To: oracle-l_at_freelists.org
> Subject: cloning a terabyte database
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> Hi
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> I had to copy a Terbayte Prod database and its test box is damanaged
> and has to recreate with Prod. What are the fastest method. Both Prod
> and Test server are at different location and so I cannot restore the
> Tape backup directly.
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> TIA
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> Sanjay
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> ______________________________________________________________________
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