Re: a practice question of backup & recovery

"Anton Buijs" <aammbuijs_at_hetnet.nl> wrote in message news:ua67cuvNBHA.295_at_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.
>

I disagree, because the question explicitly states 'if you need to recreate the controlfile AS PART OF database recovery'.

You're already in a recovery scenario, needing to re-create the controlfile. By that stage it is far too late to worry about actually *starting* to make a backup of the controlfile.

Of course you need backups *before* getting into a recovery scenario. But even then, you don't need to "close the database to user access" to make one, binary or text.

Regards
HJR
>
> 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
> > >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
>
>
Received on Thu Sep 06 2001 - 15:32:20 CDT