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What do the docs say? Look there first and if you are unsure come back and ask about what you don't understand.
If there is an option to do the same thing in a different way it's usually because one way may suit some people and the other way will suit others...So it depends on your application, your business requirements, how critical you system is and how much risk you are willing to take, etc, etc, etc.
As per oracle docs,
RMAN incremental backups back up only datafile blocks that have changed since a specified previous backup.
RMAN> BACKUP INCREMENTAL LEVEL 1 DATABASE;
Incrementally Updated Backups feature lets you avoid the overhead of taking full image copy backups of datafiles, while providing the same recovery advantages as image copy backups.
RECOVER COPY OF DATABASE WITH TAG 'incr_update';
BACKUP INCREMENTAL LEVEL 1 FOR RECOVER OF COPY WITH TAG 'incr_update'
There is a full backup, Level 0, 1 and incremental backup can be either 0 or level 1, there is an incremental backup which can be incremental differential and incremental cumulative but there is no such "INCREMENTALLY" backup in RMAN. Which 1 is good ? Incremental is good because it backups changes since the last backup, also use block change tracking for good performance which is also now available in 11g for standby databases.
Edited by: Karan on Jan 24, 2013 1:52 AM
I think some other posters have forgotten that RMAN has a feature where copies of datafiles taken with RMAN during a backup can be incrementally updated at a later date.
So a better answer to the original question would, I think, go on these lines.
An incremental level 1 backup is one that backs up only those blocks which have changed since the last level 0 or full backup, for example. That's just:
The idea is that you only back up anything that's changed, so the backup is quicker.
backup incremental level 1 database
On the other hand, an incrementally updated backup is where you first take an image copy of a file:
And then you subsequently 'refresh' that image copy by (basically) recovering it:
backup tag 'MYDB' for recover of copy with tag 'MYDB' database plus archivelog delete input;
(I'm doing the commands from memory, so I apologise if they can't exactly be cut-and-pasted).
recover copy of database with tag 'MYDB';
The recover command applies redo to the image copies of the files so that they are brought more up-to-date. The idea being that during a real recovery of the actual database, you can restore a quite-recent copy of a file and apply a little redo, rather than restore a very old copy and apply a lot of redo.
Image copies can be slow and painful to take every night, of course. This technique allows you to take one infrequently, but to maintain it as a working fresh copy by incrementally refreshing it.
So the idea of an incrementally updated backup is not to reduce backup time, but to reduce recovery time.
Edited by: Catfive Lander on Jan 23, 2013 9:06 PM
Just realised vlethakula wrote almost exactly the same thing as me. Apologies for duplicating.