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RE: Diff between "controlfile autobackup" and "snapshot controlfile"

From: Marquez, Chris <>
Date: Thu, 3 Feb 2005 14:50:04 -0500
Message-ID: <>

Diff between "controlfile autobackup" and "snapshot controlfile"

All of my next comments are from the perspective that you are NOT using = a RMAN Recovery Catalog database.

>>snapshot controlfile

>> There is no difference.
>> both produce a backup of controlfile
>> which can be used to recover database

This is a naive statement.

Every thing about RMAN and (backup/current) controlfiles has everything = to do with "time" and "accessibility".
It's the classic "chicken-n-egg" scenario.

Only a valid controlfile that exists after the end of the RMAN backup = ("time")
is available after the loss of all current controlfiles = ("accessibility")
has ANY USE!

You will note that the "snapshot controlfile" has date time stamp equal = to the being of your RMAN backup session and is NOT subsequently = updated.
As Jared pointed out it is used to freeze the controlfile at a point in = time...a ""snapshot".
This implies that RMAN need consistent information for some internal = processing?...don't know?
Since this "snapshot controlfile" is never updated it then knows nothing = of the RMAN backup that has just completed and thus can not be used to = restore the RMAN backup for which is was generated. Simply, the "snapshot controlfile" is not for you, but for RMAN = processing (might be useful for old backups).

So you move on to making your own "controlfile backups". It critical to note that "controlfile backups" are needed for to = reason's;
1.) You must have controlfiles for you database 2.) In the case of RMAN, the controlfile *IS* your backup data = repository...Meta Data about previous backups before its creation.

All of my next comments are from the perspective that you have lost ALL = live database controlfiles.

Effectively I'm backing up my "Backup Meta Data" at the end of each RMAN = backup.
My RMAN shell scripts look like this;
backup archivelog all delete input... (logs between backups) backup database...
backup archivelog all... (logs during backup) copy current controlfile to...

I'm not saying do not use these other options, just be sure you know = what your getting...what Restore & Recovery options with be available to = you.
Simply, test, test, test, your backups!
You will know the true value of your controlfile backups if you blow = away all the current one's
I was often fooled about my ability to restore until I was forced to = restore ALL of my controlfile from my RMAN backups.

Backup is Restore & Recovery that hard!


Chris Marquez
Oracle DBA
HEYMONitor=99 -
"Oracle Monitoring & Alerting Solution"

-----Original Message-----

From: on behalf of Sam Reddy
Sent:	Wed 2/2/2005 4:25 PM
To:	Oracle L (E-mail)
Subject:	Diff between "controlfile autobackup"  and "snapshot =
Hi All,

What's the difference between "controlfile autobackup" and "snapshot = controlfile" in RMAN configure ? Both are controlfile backups, what the = difference between the controlfiles they backup ? Why there are two of = these options ?

Thank you all





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Received on Thu Feb 03 2005 - 14:55:06 CST

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