Hi Deepak,

On 23/12/2009, at 05:41 , deepak wrote:

> I am newbie to backup and storage domain and trying the understand certain 
> concept of rman backup.
> 
> 1) What is the difference between a hot backup and cold backup ?

A hot backup is one where the database is backed up while it is active and 
available for use. A cold backup, on the other hand, is a backup with the 
database completely shutdown and unavailable.

Cold backups allow for the "easiest" recovery process, but at a disadvantage 
that (a) you've got the database shutdown for the entire backup window and (b) 
depending on the database, you may not be able to do a point in time recovery 
from a cold backup - you can recover only to the point it was backed up.

> 2) how rman figures out that the given backup file belongs to which datafile, 
> tablespace or database.

Being an Oracle supplied tool, I can't comment on how RMAN works through the 
mappings, but it does.

As far as its relationship with NetWorker goes, you'll either store backup 
details in the control files of the database being backed up, or you'll use a 
recovery catalogue database. In either instance though, RMAN stores details 
which, via the NetWorker supplied API (as part of the Oracle module) that 
allows mapping between the RMAN backup details and NetWorker savesets, so that 
it knows which savesets to request for recovery purposes.

> 3) How it maps the rman blocks with the actual datafile blocks while 
> restoring.

RMAN will do a standard recover/restore process - pulling backup the 
datafiles/archive logs/etc required for a recovery, then rolling forward 
logs/etc to achieve consistency in the recovered files.

Cheers,

Preston de Guise.

--
Preston de Guise

http://www.enterprisesystemsbackup.com          "Enterprise Systems Backup and 
Recovery: A corporate insurance policy"
http://nsrd.info/blog                                           NetWorker Blog
http://iamtheanticloud.wordpress.com                    Confused about Cloud? 
Get a fresh opinion here


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