Media recovery when using an old controlfile

I stand corrected - thanks.

I'm going back to boat building - I'm no good at this Oracle stuff :o)

Cheers,
Norman.

-----Original Message-----
From: Arcangelo [mailto:arcangelo-c_at_yahoo.com] Posted At: Wednesday, June 25, 2003 2:13 PM Posted To: server
Conversation: Media recovery when using an old controlfile Subject: Re: Media recovery when using an old controlfile

"Norman Dunbar" <Norman.Dunbar_at_lfs.co.uk> wrote in message news:E2F6A70FE45242488C865C3BC1245DA703D46AF5_at_lnewton.leeds.lfs.co.uk...
> Morning Jurjen,
>
> I've never had to do one, and as far as I can remember, I've never
even
> tried one, but assuming you are running in archivelog mode, then
> attempting a recovery with an OLDER version of the control file is
going
> to leave you somewhat bolloxed !
>
> The controlfile(s) should never be restored if you wish to recover
> database because the current controlfile has the SCN number that is
the
> current one. The old control file will have the old one. I've no idea
> whether Oracle will let you actually do this (and to be totally
honest,
> I've got no time to try it out !)
>
> On the other hand, maybe I missed the point of your question !
>

I've missed the subtleties of the original post, but a couple of points:

Oracle does of course allow you to use an old controlfile to perform a recovery. What else would you expect to be able to do if a disk failure took
out all your controlfiles and a datafile?

(Of course, multiplexing the controlfile should stop this happening, but I've seen many sites where you are told 'of course we multiplex them', only
to discover that one copy is on C: drive, one is on D: drive, and both C and
D are partitions on the same physical disk!).

The command 'recover database using backup controlfile' allows you to perform a complete recovery with an old controlfile. 'recover database until
cancel using backup controlfile' allows you to do an incomplete recovery using an old controlfile.

In either case, the 'using backup controlfile' clause simply tells your server process not to bother reading the controlfile's SCN to determine the
'age' of the database, but to look at the datafiles themselves to find the
highest possible SCN... that will be the point to which a complete recovery
is then performed, for example.

Despite some posts I've seen here, the 'using backup controlfile' clause never needs to be supplied unless you've actually restored a binary backup
of that file prior to starting recovery. But in a total loss of controlfiles
scenario, it may well be that that's exactly what you have to do.

As to the original poster's question, I can't tell. He says he did a 'sort
of' shutdown abort, but that actually consisted of copying the datafiles!!
Don't even pretend to know how a copy can look like a shutdown abort.

Anyway: the error 'but OPEN RESETLOGS would get error below ORA-01194: file
1 needs more recovery to be consistent' invariably means that not all datafiles were restored for the purposes of an incomplete recovery. Therefore, a (or possibly several) datafile(s) is/are at a time ahead of where the incomplete recovery is halted, and since they can't be rolled backwards in time, the database is doomed to be forever inconsistent. I suppose you could try a select from v$datafile_header to see what the SCNs
are at, and check the copying procedures to make sure you haven't forgotten
something.

;-* Received on Wed Jun 25 2003 - 09:23:16 CDT