RE: RMAN Incremental backups.

Can someone explain why incremental backups are only valid in archivelog mode?  I don't think this is correct and the manual states that consistent incremental backups are possible.  I took the quote below from the Oracle 8i Recovery Manager Users Guide and Reference Chapter 5.

"You can make consistent or inconsistent incremental backups of the database or individual tablespaces or datafiles."

I think the confusion has come between incremental backups, and inconsistent backups.  The two concepts are quite different and are in fact orthogonal.  That is, I can have incremental backups which are consistent or inconsistent, and similarly I can have full backups which are consistent or inconsistent.  In fact a full backup is nothing more than an incremental level 0 backup.

I see no reason why I cannot restore a set of consistent incremental backups without the need for recovery and the archived redo logs.  That is, if I take the last consistent level 0 backup and apply all of the appropriate consistent incremental backups I am left with a consistent database that does not need recovery and can be opened.  This makes sense because each incremental backup has a copy of the blocks that have changed since the last incremental backup (ignoring levels for simplicity) and these blocks are consistent as at the time that database was shutdown even though not all blocks are included in the backup.

On the other hand, if the incremental backups were inconsistent (i.e., the database was open while the backup was being taken) I would have to perform some recovery (that is, apply the redo logs to bring the database up to date).  Or if I am missing an incremental backup, I would have to also apply redo logs.

All comments welcome.

Cheers,
Craig.

-----Original Message-----
From: Mercadante, Thomas F [mailto:Thomas.Mercadante_at_Labor.State.Ny.Us] Sent: Thursday, 7 February 2002 5:18 AM
To: Multiple recipients of list ORACLE-L Subject: RE: RMAN Incremental backups.

Prasad,

Incremental backups are only valid if your database is in ARCHIVELOG mode. Think about it - to be able to recover using incremental backups, you *Need* the archivelog files to apply changes.  These are not being created when you are running in NOARCHIVELOG mode.

Secondly, flipping between ARCHIVELOG and NOARCHIVELOG to perform Rman backups is a *total* waste of time.  Again, you will not be able to use the backups to restore your database (except for the MOUNT/cold backups).

Your choices are:
Run in NOARCHIVELOG mode, and perform MOUNT/Rman or cold database backups. Run in ARCHIVELOG mode and perform Rman/database open backups.

or use older-style non-Rman backup methods.

I would not be flipping a production database back and forth between ARCHIVELOG/NOARCHIVELOG mode just to use Rman.  Makes no sense.

Hope this helps.

Tom Mercadante
Oracle Certified Professional

-----Original Message-----
[mailto:Prasada.Gunda1_at_hartfordlife.com] Sent: Wednesday, February 06, 2002 11:58 AM To: Multiple recipients of list ORACLE-L

Hi All,

I am new to RMAN. I am reading RMAN documentation and doing some testing on our development box.

I have couple of questions.

1. Our database is in NOARCHIVE LOG mode and I would like to do Incremental backups.      Since db is in noarchive log mode, I put the database in mount state and did the base level      and incremental backups. Looks like it worked fine.

     In one of the training documentation, it says 'Because the database is in noarchive log mode, the incrementals are      not applicable,  so use the full backup option'.

     It is contrary to what I did. Am I missing something here. please clarify me. Are the backups valid?

2. Since the database is in noarchive log mode, db is in mount state during full/incremental backup.
     I want to keep the database open if possible and would like to know if the following procedure works to
    keep the database open during the backup.

   1. Shutdown the db before backup.
   2. Bring back the db in ARCHIVE LOG mode.
   3. Perform full/incremental backups (including archive log files) while
the database is open.
   4. Shutdown the db after backup is done.
   5. Bring back the db in NOARCHIVE LOG mode.

   I am not sure whether it makes sense or not. Please pass your
suggestions.

Thanks in advance for your suggestions.
Best regards,
Prasad

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