Re: a practice question of backup & recovery

It's a lousy question, since it asks 'in which ways' when it's really wanting to know 'when'.

In practice, if you knew you needed to recreate the controlfile, you'd go for option D, because the trace file is the easiest way of pulling that particular trick off. But I guess their point is that an existing trace file might be out of date, and therefore, before shutting the database down, you'd issue a new 'backup controlfile to trace' to make sure it was bang up to date.

Unfortunately, in doing so, you are compromising your ability to recover, since about the only time I can think of when you perform a recovery requiring a new controlfile is when someone has dropped a tablespace, or otherwise made a change to the structure of the database, such that the controlfile you have is describing a database structure that is incorrect. The last thing you'd want in such circumstances is an 'up to date' trace file, since that will be missing the very things you want to perform recovery to retrieve.

The only other thing I can think of is that you need to recreate the controlfile because the existing ones have become corrupted or are missing. In such a circumstance, your chances of having the option of nicely shutting down the database to prevent User access are somewhere close to zero, so again, I have no idea what they are on about with option C.

It either is an option, because the database is up and running perfectly well, just missing a tablespace or two -in which case you wouldn't want to take it. Or it isn't an option at all because your database has just crashed recognising the loss of controlfiles -in which case you can't take it even if it made sense to do so.

Correction: it's not a lousy question, it's just crappy.

Regards
HJR "Dino Hsu" <dino1.nospam_at_ms1.hinet.net> wrote in message news:vmbcpt86cufh5uree7o0sdose2h7t3i5mc_at_4ax.com...
> 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 Wed Sep 05 2001 - 15:29:15 CDT