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Re: a practice question of backup & recovery

From: Anton Buijs <aammbuijs_at_hetnet.nl>
Date: Thu, 6 Sep 2001 19:46:34 +0200
Message-ID: <ua67cuvNBHA.295@net037s.hetnet.nl>


I think I understand the question now.
Answer C is correct because if you need to recreate the control file the only way is to make a backup controlfile in advance when it is mounted or open.
But I'am an Oracle DBA, not a lawyer. And English is not even my native language.

Anton Buijs <aammbuijs_at_hetnet.nl> schreef in berichtnieuws ebgImgjNBHA.300_at_net037s.hetnet.nl...
> The question does not mention a clone situation so I can't take that into
> consideration for the answer.
>
> That creating the controlfile has to be the first step in a recovery
process
> in clear: without a controlfile no mounted database.
> So: answer A is impossible.
>
> As far as my knowledge goes (with 10 years Oracle DBA experience, just
> passed for the Oracle 8 Backup and recovery OCP exam):
> 1. To be able to create a new controlfile ('alter database backup
> controlfile to trace (or to <file>) the db must be mounted or open. (Test
on
> a nomounted db gives ORA-1507).
> 2. If I can create a new controlfile from a mounted or open database this
> implies the current controlfile is valid, so why would I need a new
> controlfile?
> 3. If I need a new controlfile this implies the current ones are all
damaged
> or lost so I can't mount the db anymore and therefore I can't make it from
> the db anymore.
> So: answer C is impossible. Apparently I must be overlooking something
here.
>
> Anser D assumes I have a backup controlfile made before this situation
> occured (to trace or to file, does not matter). So it is possible but
> requires an assumption.
>
> But answer B is also possible: before the tapes are restored I have a lot
of
> time to manually type in a script that does a 'create controlfile ......'
.
> After using it I can apply the redo logs (assuming archived redo logs and
> the database is running in archive log mode)
>
> When I check the book (A76993-01 Backup and Recovery Guide Release 2
> (8.1.6), Chapter 6 - Media Recovery Scenario's, Loosing all copies of the
> current controlfile) the only way to recover is using a 'backup
controlfile
> to file' file, create an new one using the (if necessary adjusted)
statement
> from 'backup control file to trace' file or manually type in the create
> controlfile statement again - which is almost impossible because I must
know
> the filename's belonging to the file id's (that is: in the order the
> datafiles where added to the database).
>
> I don't say the OCP exams should be easy. A difficult exam make the
> "Certified DBA" certificate more valuable.
> But it are these kind of questions that makes it nasty.
>
> Anton Buijs
>
> Reid Lai <reidlai_at_netvigator.com> schreef in berichtnieuws
> 3B965D91.D009C355_at_netvigator.com...
> > How about your control file was corrupted? Or you need to do physical
> > cloning?
> >
> > Cheers,
> >
> > Reid Lai
> >
> > Dino Hsu wrote:
> >
> > > Dear all,
> > >
> > > A practice question:
> > > If the DBA must re-create the control file as part of database
> > > recovery, in which of the following ways should it be done?
> > > A. After backup datafile restoration
> > > B. Between restoring backups and applying redo logs
> > > C. Before closing the database to user access
> > > D. Using the script containing the create controlfile command in the
> > > trace directory
> > >
> > > The answer is C,
> > > Explanation: This question is tricky, and requires careful reading of
> > > the question as well as thorough knowldege of the Oracle database
> > > recovery process. Creation of a control file for the database recovery
> > > process should be accomplished first. The other choices are all
> > > incorrect becasue they place the creation of control files later in
> > > the recovery process.
> > >
> > > I cannot remember any scenario that requires creating a copy of
> > > controlfile first although there are some which do recovery when
> > > controlfiles are missing or damaged. Your comments are highly
> > > appreciated.
> > >
> > > Dino
> >
>
>
>
>
>
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>
Received on Thu Sep 06 2001 - 12:46:34 CDT

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