Re: Backup Controlfile and ArchiveLog
- From: Hemant K Chitale <hkchital@xxxxxxxxxxxxxx>
- To: jeremy.schneider@xxxxxxxxxxxxxx
- Date: Sat, 05 May 2007 01:11:58 +0800
I just saw your posting at
http://www.ardentperf.com/2007/05/04/recovering-your-controlfile-without-a-backup
You didn't actually "recover" the controlfile.
You really "restored" it.
You had done a shutdown abort of the database.
The datafiles were not in sync. The Recover command looks at all the
datafile headers and realises that some datafiles are "ahead" of the
others. The Recover command, then, DOES need an ArchiveLog (or the
active online redo that hadn't been archived yet -- faking it is as
an ArchiveLog).
You were testing a specific scenario where the controlfiles were
deleted when the instance were running.
Test the scenario where the the database is shutdown normal/immediate
(or even a RECOVER has been completed without an OPEN) -- then
restore or recreate controlfile and try a RECOVER. See if you can
just do a CANCEL there.
At 12:43 AM Saturday, Hemant K Chitale wrote:
Interesting..
Question : In your recovery testing, what was the exact sequence ? Was it ?
a) Restore an older controlfile binary backup -- only
controlfile restored, datafiles being current
b) Issue RECOVER DATABASE USING BACKUP CONTROLFILE -- did you
also specify "UNTIL CANCEL" ?
OR
a) Create Controlfile
b) Issue RECOVER DATABASE ... commands.
What if you had also restored DataFiles from the older backup ? --
ie even the DataFiles
were not "current" ? Then, if that was a Hot Backup, you would have
had to apply
some ArchiveLog(s). If it was a Cold Backup, ... (ie ControlFile
and DataFiles from Monday)
you should have been able to CANCEL and OPEN RESETLOGS without having
any online redo log file (as today when you do the restore, it is
Wednesday so your
ondisk online redo logs are Wednesday's files).
Hemant
At 10:36 PM Friday, Jeremy Paul Schneider wrote:
Related to this... we were testing some recovery scenarios for a
"tech night" this past monday night and walked through controlfile
recovery among other things...
Even if you have a clean database shutdown (immediate) and restore
*only* your controlfiles, we found that you still need to process
the last online redo log then open with resetlogs. If you just say
CANCEL then it won't open the database. This is interesting
because your datafiles do not actually need recovery. However
Oracle makes you process that last online log and open with
resetlogs. My theory is that Oracle doesn't actually update the
SCN in the control file until it "recovers" a logfile... even if
there's nothing in that logfile to actually process...
FYI, we were testing on <http://10.2.0.2>10.2.0.2
-Jeremy
Hemant K Chitale
http://web.singnet.com.sg/~hkchital
and
http://hemantscribbles.blogspot.com
and
http://hemantoracledba.blogspot.com
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