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Re: why r more archives generated during hot backup

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Mon, 23 Sep 2002 19:47:59 +0100
Message-ID: <amnnlt$7uf$1$8302bc10@news.demon.co.uk>

Connor,

You don't need to verify it, you've got the seminar notes (Session 03 Redo: slide 25 IIRC). You have to be careful about saying things like 'flushed out by dbwr' - it might give the wrong impression. If a block is written by DBWR it (usually) stays in memory, so it doesn't get a full copy image on the next changes. If it is flushed because __another_process__ wants to use the buffer and it is subsequently re-read then, as you point out, the first update thereafter writes two redo record again - the full block image, and then the normal redo vector.

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

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Connor McDonald wrote in message <3D8F5CD0.3E69_at_yahoo.com>...

>
>I haven't physically sat down and verified, but I think its (only) the
>*first* change to the block since it is loaded into the cache. Thus you
>might get (all in hot bkp mode)
>
>- change block (whole block to redo)
>- change again (just rows to redo)
>- flushed out by dbwr
>- change same block (whole block)
>- change again (just rows)
>
Received on Mon Sep 23 2002 - 13:47:59 CDT

Original text of this message

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