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Re: RMAN internal`s mechanism

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Wed, 3 Mar 2004 10:55:11 +0000 (UTC)
Message-ID: <c24dif$57f$1@sparta.btinternet.com>

Notes in-line

-- 
Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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"Ofer Razon" <orazon_at_dbnet.co.il> wrote in message
news:74c5bf11.0403030230.1464f170_at_posting.google.com...

> Hi all.
>
> As far as I know, RMAN is capable to backup only the blocks that
> changed since it`s last backup.
> I`m really interested in the mechanism used by RMAN to detect these
> blocks when it runs.
> Does anyone here know how is it implemented?
>
Every block has a last change number - which is the SCN at the last change plus a counter that goes from 1 to 254. rman knows when the SCN when it last did a backup, reads each block, and checks the last change number.
> My goal is to use the same mechanism to find which blocks were changed
> since the last check.
>
Possible - so long as you knew the SCN when rman started (or perhaps when it started each file, or tablespace - that's a little detail that I'm not so sure on; the file would be the obvious choice). The last change SCN is in a fixed location in the block, so you could write some 3GL code to scan each file and pick it out from each block. I am curious to know why you want to do this.
> Ofer.
Received on Wed Mar 03 2004 - 04:55:11 CST

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