RE: Fav. Urban Legend...

Point taken... I assume you mean a cold backup in ARCHIVELOG mode... :-)

Robert G. Freeman - Oracle8i OCP
Oracle DBA Technical Lead
CSX Midtier Database Administration

The Cigarette Smoking Man: Anyone who can appease a man's conscience can take his freedom away from him.

-----Original Message-----
Sent: Sunday, March 17, 2002 6:43 PM
To: Multiple recipients of list ORACLE-L

On Sunday 17 March 2002 07:53, Freeman, Robert wrote:

> 1. You do not open the database to users until AFTER you do a backup (hot
> or cold, dosen't mater) at point t2.

Well, yeah, that was the point. It doesn't have to be a cold backup, but since you can't do any work, it may as well be a cold backup.

Jared

>
> 2. There is a method of recovering a database (8i +) after RESETLOGS has
> been
> issued with archived redo logs. I discussed it in my DBA World Tour backup
> and
> recovery presentation. To do this, you MUST have the control file for the
> database from BEFORE the resetlogs operation, and backup of the control
> file from AFTER the same operation. I've done this about 3 times in
testing
> and it works fine but it very very picky about the control file images.
>
> RF
>
> Robert G. Freeman - Oracle8i OCP
> Oracle DBA Technical Lead
> CSX Midtier Database Administration
>
> The Cigarette Smoking Man: Anyone who can appease a man's conscience can
> take his freedom away from him.
>
>
>
> -----Original Message-----
> Sent: Friday, March 15, 2002 7:28 PM
> To: Multiple recipients of list ORACLE-L
>
>
> Hi Jared,
>
> > > * You *have* to take a COLD backup of the database after using
> >
> > resetlogs.
> >
> > > (Not required - a Hot backup and archive logs is adequate. All hot
> >
> > backups /
> >
> > > archive logs prior to that are invalid, though...)
> >
> > Consider the following:
> >
> > Time:
> >
> > t0: database restored
> > t1: database opened with RESETLOGS
> > t2: hot backup started ( database in archive log mode )
> > t3: users input very important transactions
> > t4: database crashes, and must be restored
> >
> > How will you recover the transactions from time t3?
>
> As long as the online redologs are available, this should be no problem. I
> have successfully recovered databases where a log switch did not occur and
> recovery had to use an online redo log. (I am assuming that the lost
> datafiles will be restored from this hot backup fresh off the tapes)
>
> On the other hand, if the online redolog is hosed you have lost the
> transactions anyway, _regardless_ of the fact that a Cold backup was
taken.
> Then you will have to go back to the _previous_ incarnation and redo the
> restore and then perform a ccf/resetlogs (i.e. back to square one). If you
> have a Cold backup, you restore the cold backup and go on with life. I.e.
> in both cases (availability of cold or hot backup, lost online redo log),
> you have lost transactions...
>
> Additionally, with a Hot backup and depending on what was lost, you can at
> least perform tablespace/datafile recovery . With a cold backup, you will
> have to restore the whole database....
>
> The point I was trying to make was that a Cold backup after a RESETLOGS
> does not serve anything. Maybe there is still a gotcha I have not been
able
> to figure out, so Backup/restore Gurus: take a bash at this logic! I would
> love to be corrected.
>
> (Btw, the previous recovery scenario was on 7.3.4 - things could have
> changed since, and I have not been able to test that out...)
>
>
> John Kanagaraj
> Oracle Applications DBA
> DBSoft Inc
> (W): 408-970-7002
>
> Grace - Getting something we don't deserve
> Mercy - NOT getting something we deserve
>
> Click on 'http://www.needhim.org' for Grace and Mercy that is freely
> available!
>
> ** The opinions and statements above are entirely my own and not those of
> my employer or clients **

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Author: Jared Still
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Author: Freeman, Robert 
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