A Question for the Gurus

[oracle0]

I was asked by some personnal in an interview this question.

When will I have to recreate the database ? In that failure no recovery is possible. Assuming database in Archivelog mode and backup exists.

[rohitsn]

Hi
Can you please elobrate on this question.
Regards
Rohit S nirkhe

[kris109]

The extreme situations for database recreation are:

1. Lost all control files
2. Lost or deleted some datafiles
3. Lost all redo logs
4. Gap in archived logs with some archived logs missing
5. Corrupt files in backup.

But as you work with oracle, you realize that it is extremely rare to throw a database out the window and start from the scrach. Life is not that bad and you always can recover something.

1. You can recreate control
2. You can take the offending datafile offline and open the rest of the database
3. Recover the database from last valid backup
4. Can do partial recovery with available archived logs if a valid backup exists
5. Recreate the control file with only those datafiles that are not corrupt and open the database from backup control file.

Of course if the machine had caught fire, then you have to recreate the database.

[DaPi]

I think you could say that if you are restoring & recovering a db from backups & archlogs, you do not need "recreate" it. Only those who insist on export/import for backup/recovery have to run a CREATE DATABASE command.

[marist89]

Originally posted by oracle0
I was asked by some personnal in an interview this question.

When will I have to recreate the database ? In that failure no recovery is possible. Assuming database in Archivelog mode and backup exists.

If you have an adequate backup/recovery plan, never.

[kausik_m123]

It depends on the kind of backup u have if its an offline or cold backup then u place the files in the right location.Do a media recovery.
If its required recreate the instance thats it , no need to recreate the DB.
Incase u have a Online backup (dump file output of an exp utlity) taken on user mode.And some of the datafiles as well as control file is missing.
Then only it becomes necessary to recreate the DB and import the dump .Actually recreating DB can be bypassed(in case u have the datafiles/control files etc in proper location) in that case also by dropping the user and importing the dump is sufficient enough.

The most important thing is that to have a consistent backup. Today downtime of DB has become a great concern which leads to introduction of replication/standby DB.

Kaushik

[thanigai]

ANswer to your question...
If backup exists and the databsase in Archivelog mode...no need to recreate the database..Just restore from backup and startup them..

Thanks,
Thanigaivasan.