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Re: UNTO TBS behavior in 9i

From: Daniel W. Fink <daniel.fink_at_optimaldba.com>
Date: Fri, 26 Jan 2007 14:22:22 -0700
Message-ID: <45BA710E.8040800@optimaldba.com>


It has been a few years since I did that work, so my recollection may be a little rusty. If I am wrong or missing something, fellow oracle-l mates...jump in!

An insert append uses new blocks, so there is nothing in the block to start with. When the insert append is finished, these 'new' blocks are associated with the table by updating the high water mark/segment information. To undo the insert append, Oracle never associates the block to the table. If one of those blocks is needed later, it is 'renewed' (assuming it was written to disk).

Regards,
Daniel Fink

NEW pop.tiscali.de wrote:
> Hi Daniel,
>
> I read through your paper. Thanks for the info. To be honest, 50% of
> it went over my head :-(
>
> From experence though, I know that insert append creates must less
> UNDO than an insert into a table that's had many deletes. My
> assumption (obvious wrong - thank's for the pointers from the better
> informed), was that the before image was saved. This made sense to
> me: there is no before image for an insert append, just the blk
> addresses would be needed for a delete in case of a rollback - hence
> the decreased UNDO. I see from your paper that this is not the
> case. So can you please explain to me, why an insert append causes
> less undo.
>
> Tony
>
>

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Received on Fri Jan 26 2007 - 15:22:22 CST

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