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Re: Recovery. Have you been there before???

From: Thomas Kyte <tkyte_at_us.oracle.com>
Date: Tue, 01 Dec 1998 16:02:24 GMT
Message-ID: <36680be7.92047066@192.86.155.100>


A copy of this was sent to "Igor " <espiaui_at_hotmail.com> (if that email address didn't require changing) On 1 Dec 1998 11:40:27 GMT, you wrote:

>Suppose there was an earthquake and you lost your production machine today
>(Thursday).
>You have a COLD backup from last Sunday and a HOT backup
>from yesterday(Wednesday) + all the necessary archived log files.
>There is an identical(same configuration) brand new machine
>waiting for you to recover from your backups.
>
>I would like to know:
>
>1)What is the quickest way for recovery??

if you don't care about lost data from sunday to wednesday, restoring the cold backup is fastest and easiest.

If you care about it (the data from sunday to wednesday) then only the hot backup counts.

>2)Can I recover by using the hot backup only. If so how do I
> recreate the physical on-line redo log files as they are never part of
> an on-line backup?

you'll recover until cancel (for example), apply the archived redo logs until you've applied them all and then open the database with resetlogs to get them (the online logs) recreated. you will lose the data that was in the online redo logs and not yet archived safely (which is a good reason to have reasonably sized redo logs -- on the order of megabytes -- to prevent the loss of mega data...

>3)When backing up the datafiles as part of the hot backup, do
> I need to include rollback segments and temp datafiles?
>

rollback segments - YES, YES and YES. Absolutely. No if and or buts about it. rollback is used during recovery (we roll forward and then roll back from rollback during recovery)

temporary tablespace -- you can get away without them if they are true temporary tablespaces (of type temporary) but I would recommend against it. They are typically a small percentage of the total backup size and are pretty easy to backup. Also, during a recovery (eg: during the emergency when things must/should go as easy as possible) you want as few steps as possible. Recreating your temp and working around the fact they are not there would just complicate things. So -- you can skip them but you should practice recovery on another machine without them to get the proper steps down to a science.

>Thanks in advance
>Igor
>
 

Thomas Kyte
tkyte_at_us.oracle.com
Oracle Government
Herndon VA

--
http://govt.us.oracle.com/ -- downloadable utilities  



Opinions are mine and do not necessarily reflect those of Oracle Corporation  

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