Re: Question about Archivemode

"Howard J. Rogers" <howardjr2000_at_yahoo.com.au> wrote in message news:ah50fu$ipc$1_at_lust.ihug.co.nz...
>
> "Ryan" <rgaffuri_at_cox.net> wrote in message
> news:H1nZ8.92774$%%2.3974480_at_news2.east.cox.net...
> >
> > "Howard J. Rogers" <howardjr2000_at_yahoo.com.au> wrote in message
> > news:ah4rcd$en2$1_at_lust.ihug.co.nz...
> > >
> > > "Howard J. Rogers" <howardjr2000_at_yahoo.com.au> wrote in message
> > > news:ah4r3k$ecu$1_at_lust.ihug.co.nz...
> > > >
> > > > "Ryan" <rgaffuri_at_cox.net> wrote in message
> > > > news:R4lZ8.92701$%%2.3951689_at_news2.east.cox.net...
> > > > > Ok this is a really basic Backup and Recovery question.
> > > > >
> > > > > If someone drops the system tablespace, ie, an intruder.
> > > > >
> > > > > Is it possible to perform a backup from the redo logs
> > > >
> > > > I'll stop you right there, and say that the question as posed
doesn't
> > make
> > > > sense. You don't backup anything 'from' the redo logs. You use redo
> logs
> > > to
> > > > recover a copy (ie, a backup) of a datafile.
> > > >
> > > > >in you are not in
> > > > > archive mode or have any software like RMAN installed? Or do I
have
> to
> > > > > recover from my last cold backup?
> > > > >
> > > >
> > > > The rules are exactly the same, whatever tablespace you are talking
> > about
> > > > (with the exception of temporary tablespaces). SYSTEM is no
different
> > from
> > > > DATA or TOOLS in this respect. Either you can apply an uninterrupted
> > > stream
> > > > of redo from the time a backup of the datafile was taken to the time
> the
> > > > rest of the database is at, or you can't.
> > > >
> > > > If you're not in archivelog mode, then the chances of you being able
> to
> > > > supply such an uninterrupted redo stream is vanishingly small.
> > Therefore,
> > > > you won't be able to bring the backed-up datafile into synch. with
the
> > > rest
> > > > of the database, and therefore the database can't be made to
function
> > > > properly.
> > > >
> > > > How then do you get the database consistent and useable? By
restoring
> > the
> > > > entire database from your last cold backup, as you say.
> > > >
> > > > There is one scenario where, despite not being in archivelog mode,
you
> > > might
> > > > get away with a complete and perfect recovery: if the continuous
> stream
> > of
> > > > redo you require still happens to be sitting in the online logs. If
> you
> > > have
> > > > 5 online redo log groups, which switch every half hour, then you
have
> > 2.5
> > > > hours of redo available to you. So if you backed up last night,
opened
> > the
> > > > database at 9.00am, and the intruder swiped the system tablespace at
> > > > 11.00am, you're doomed.
> > >
> > > BONG! I meant to say 12.00 noon.... you've 2.5 hours of redo
available,
> > and
> > > he swipes it three hours after the database is opened... *then* you're
> > > doomed. 11.00am would be OK, because (despite my pathetic maths)
that's
> > only
> > > 2 hours after being opened for business, so the required redo should
> still
> > > be available.
> > >
> > > Sorry. (Walks away muttering to himself.... "9+3=12, not 11", "9+3=12,
> not
> > > 11")
> > >
> > > Regards
> > > HJR
> > >
> > > >But if he swiped it at 9.45am, the redo required to
> > > > recover the backup of the system datafile is still available in the
> > online
> > > > logs, so you could just restore that one file and do a recovery on
it.
> > > >
> > > > Clearly, there's no guarantees, though, that the required redo would
> be
> > > > available. Only archivelog mode can make that guarantee.
> > > >
> > > > Regards
> > > > HJR
> > > >
> > > >
> > > > > For those of you who saw an earlier post of mine... no this did
not
> > > > happen.
> > > > > :)
> > > > >
> > > > >
> > > >
> > > >
> > >
> > >
> >
> > thanks howard... my articulation is atrocious.. I meant use the redo
logs
> to
> > recovery. Sorry, but thanks for the explanation... didnt recall it in
all
> > that much detail.
> >
> > Another question. We are using a tape backup. I do not know how these
> things
> > work. If the database was to get destroyed for some reason, but the hard
> > drive is good.. will I need to reformat the hard drive and reinstall all
> > oracle products to get my backup with a tape or can I just grab the
> > datafile, redo log files, control files... etc..
>
>
> It entirely depends on what you mean by "the database is destroyed". If
you
> mean someone has wiped all datafiles, online redo logs, controlfiles and
> on-disk archives, but otherwise the hard disk is functioning fine, then
> there's no need to wipe it and re-install Oracle. You just restore the
> datafiles, re-create the controlfile and open with a resetlogs. If you've
> been taking cold backups because you are not in archivelog mode, then you
> may well have the online logs included in your backups... so you can
restore
> them, too, and re-create the controlfile, and open the database without a
> resetlogs.
>
> I suppose, though, the real question is how the stuff got onto your backup
> tapes in the first place. If you've used RMAN to put them there, then
things
> get very interesting indeed. Assuming you are using RMAN with a recovery
> catalog, that catalog needs to be recovered itself before you can use RMAN
> to read the tapes containing your main database files. But if all you've
> been doing is using something like backup exec or arcserve to backup the
> files onto tape, and assuming those programs are still functioning, then
you
> just restore the database files like I said.
>
> Short of user stupidity, it is practically impossible to wreck an Oracle
> database to such an extent that you would lose absolutely everything. Even
> in noarchivelog mode, it is always possible to get something working
again.
> You might lose some data, depending on how old your backup was, but you'd
> have to be criminally incompetent to mangle things so severely that I lose
> the lot, utterly, and completely, and without possibility of some sort of
> recovery.
>
> Regards
> HJR
>
>
>
> >
> >
>
>

What if your using a nightly DOS shell script to shutdown the database and copy it to a tape. It is not in archivelog mode. Nothing is mirrored. There is one hard drive.

If I have to restore the database, will I be able to simple get the datafiles, control files etc... from the tape backup and place them into my oracle home, then do an instance recovery?

Is there a one line command of somethign you can drop or delete that will make a database unusuable until you perform a cold backup assuming the above scenario? Received on Wed Jul 17 2002 - 19:45:25 CDT