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Re: rollback after crash

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Wed, 14 Dec 2005 16:08:47 +0000 (UTC)
Message-ID: <dnpg2f$cv5$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com>


"Pradeep" <agarwalp_at_eeism.com> wrote in message news:1134574000.974721.270670_at_g43g2000cwa.googlegroups.com...
> Thought of this situation while going through one of the threads on
> asktom on checkpoint.
> Suppose
> - uncommitted data is flushed to the disk and
> - corresponding rollback is also flushed
> - corresponding redo is later overwritten
> - instance crash.
>
> How does it recover now ?? or how does is rollbacks the uncommitted
> data that is on the disk.
>

If the transaction is uncommitted, then the rollback will be held open, and cannot be overwritten (undo segment header will have a transaction table slot in state 10).

In the event of a crash, any redo that has to be re-applied will still leave the transaction visible as an uncommitted transaction in the rollback segment header.

So the transaction will be rolled back.

-- 
Regards

Jonathan Lewis

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Received on Wed Dec 14 2005 - 10:08:47 CST

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