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Re: Backing up Online Redo Logs

From: Thomas Kyte <tkyte_at_us.oracle.com>
Date: Wed, 20 Oct 1999 09:07:52 -0400
Message-ID: <Tr0NOAVdPnDFXhQuuNaN8mz0+Ouu@4ax.com>


A copy of this was sent to happychappy_at_my-deja.com (if that email address didn't require changing) On Wed, 20 Oct 1999 07:33:09 GMT, you wrote:

>
>
>Hi I'm just about to test my hotbackup of a 7344 instance, I've
>put copies of my datafiles (produced whilst in backup mode), my
>archive-logs and control-files onto a clean machine, but is it
>feasible to just put copies of my online redo-logs over, common
>sense indicates that they're being continually updated and so doing
>a Unix copy of them will probably produce an inconsistent image, yet
>I can find no documentation on how to backup an online-redo log.
>

you never backup an online redo log -- thats why the documentation on how to is 'lacking'.

From the backup section in the admin guide:



• If you want a copy of the current online log, then archive it. Archiving means the online log will no longer be the current log. If you end up copying a current online log, the copy will appear as the end of the redo thread. However, additional redo may have been generated in the thread. If you ever attempt to execute recovery supplying the redo log copy, recovery will erroneously detect the end of the redo thread and prematurely terminate, possibly corrupting the database.

so, after you've done the hot backup -- archive the current online redo log and then backup the archived redo log.

>So on a clean machine is the only thing I can do is a point-in-time
>recovery with a reset logs option ??

if you do not have the online redo logs from the other instance -- it'll be more like a recover until cancel with an open reset.

Typically you will have your online redo logs duplexed or triplexed -- reducing the probability of data loss in a catastrophic failure. It is expected that some copy of the online redo logs may survive. If all copies of the online redo logs are missing during media recovery -- you will only be able to recover as far as the archives go.
>
>
>Sent via Deja.com http://www.deja.com/
>Before you buy.

--
See http://osi.oracle.com/~tkyte/ for my columns 'Digging-in to Oracle8i'... Current article is "Part I of V, Autonomous Transactions" updated June 21'st  

Thomas Kyte                   tkyte_at_us.oracle.com
Oracle Service Industries     Reston, VA   USA

Opinions are mine and do not necessarily reflect those of Oracle Corporation Received on Wed Oct 20 1999 - 08:07:52 CDT

Original text of this message

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