RE: Re[1] : Recovery Scenarios - Help (did you already crash?)

From: Mark W. Farnham <mwf_at_rsiz.com>
Date: Mon, 29 Nov 2004 11:00:25 -0500
Message-ID: <KNEIIDHFLNJDHOOCFCDKMEFHFLAA.mwf@rsiz.com>

Depends. Did you crash or hang? Were any dirty blocks in the buffer cache remaining that were dependent on the log that was lost when you crashed or shut down?

Now if you had any dirty block in the buffer, crashed(losing the dirty blocks) and the online log you lost was indeed the current log (not what the poster wrote, but not too wild an assumption), then I believe you have lost all sources of producing block images consistent with a complete recovery from the existing database files. Hmm. Maybe one more out - if all the "lost" dirty blocks were from uncommitted transactions, it is possible that rollback from the UNDO could allow full consistent recovery, but you might need to write a special program to use the information in UNDO, because I *think* Oracle's recovery establishes a consistent redo point before the rollback is performed. If you've got dirty blocks at all, though, it seems likely you've got dirty blocks for UNDO, so that probably is a dead end.

Suppose for a moment that the database did not crash (yet).

Can you switch to a log that remains available or to a new log? (I haven't tested recent versions. Testdb online logs, your days(hours) are numbered!)

Will checkpoint and patience assure that your database files don't need any of the current online logs?

Your proper action might well not be a recovery at all, but rather a full hot backup (since the thread of continuous redo logs from any previous backup is lost.)

Now if the online log lost is indeed the current log and you already crashed with dirty blocks I think you're limited as Peter indicated.

Regards,

mwf

>
>>>Case 3
>>>------
>>>I have lost an un-archived online redo log file.The proper recovery pr=
ocedure is :
>>>- restore all datafiles from backup
>>>- mount the database
>>>- recover until cancel
>>>- open resetlogs
>>>
>>>Without restoring datafiles from backup,Can i do this :=20
>>>- mount the database
>>>- recover until cancel
>>>- open resetlogs
>>> =20
>>>
>
>when i recover/resetlogs without restoring the
>datafiles from backup , the database will be inconsistent
>state ... am i right ?
>
> =20
>

You will not be able to open the database since the current redolog is=20 missing.

You can get more infomation on Oracle and revovery from *Oracle9/i/=20 Backup and Recovery Concepts Release 2 (9.2),*

*Chapter 3 Recovery Principles*
****
**/peter
**

>Thanks and Regards,
>Prem.
>
>--
>http://www.freelists.org/webpage/oracle-l
>
> =20
>

--=20

Best regards / Venlig hilsen

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Received on Mon Nov 29 2004 - 09:57:46 CST