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Re: Recover deleted rows from a table from archive logs?

From: Brian Peasland <dba_at_nospam.peasland.net>
Date: Thu, 26 Oct 2006 13:35:29 GMT
Message-ID: <J7qwF6.A04@igsrsparc2.er.usgs.gov>


Steven Patterson wrote:
> On Oct 26, 2006 at 3:02am sybrandb wrote:
>
> s> Could you *please* support your statements re redolog support with
> s> references from the docs or retract this misinformation?
>
> I retract the point that not enough information is stored in the log files
> to recover deleted lines - it was based upon old information from a
> training course a long time ago, where I was told that for efficiency the
> redo logs only contained enough information to identify the deleted rows
> (and indeed, was told that this was a key limitation of LogMiner!)
> Certainly in Oracle 8i the Logminer does extract enough information to
> recover from a DELETE statement. My apologies.

Actually, you were partially correct. For a delete operation, the redo logs contain information that is basically "DELETE FROM obj# WHERE ROWID=aaa.bbb.cc.dd". So that part seems to be what you are saying. However, the redo logs also contain the changes to the undo segments. So the information to undo this operation is also there. This includes all the data to reconstruct the entire row.

Cheers,
Brian

-- 
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Brian Peasland
dba_at_nospam.peasland.net
http://www.peasland.net

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Received on Thu Oct 26 2006 - 08:35:29 CDT

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