Re: Shutdown Abort and Backup

From: Matthias Gresz <GreMa_at_t-online.de>
Date: 1998/03/02
Message-ID: <6ddopm$l89$1@news02.btx.dtag.de>#1/1

On Sun, 1 Mar 1998 21:33:31 -0000, "Doug Burns" <dougburns_at_email.msn.com> wrote:

>After years I still don't have a good technical answer to the following ....
>
>Assumptions
>-----------------
>1. In the event of a power failure, the information in the online redo log
>files
> will allow automatic instance recovery to take place
>
>2. Likewise, in the event of a SHUTDOWN ABORT, smon will perform instance
> recovery on STARTUP
>
>(These two assumptions are based on every example I have seen, but I would
>be interested in any experiences which contradict my own)
>
>Question
>-------------
>So, why do Oracle insist on a clean shutdown before a backup. Won't a backup
>taken after a shutdown abort contain files in the same state as a database
>after a power failure? Are Oracle suggesting that a database might not be
>re-startable after a SHUTDOWN ABORT?

If you backup this way you'll always had to restore also your online redo logs to be able to recover automatically. So you'll never be able to recover you db close to point it crashed. Assuming your db is running in archive mode and you've three online redo logs your state while backing up will be:

archive logs 		redo logs
	230		231
	229		232
	228		233
	...

CRASH

archive logs		redo logs
	410		411
	409		412	
	408		413
	...

After your restore

archive logs		redo logs
	410		231
	409		232	
	408		233
	...

How to recover now? You'll only be able to recover till log 233. All further changes will be lost.

For bringing down your db to backup try this:

CONNECT <user>/<pwd>
SHUTDOWN IMMEDIATE;
STARTUP RESTRICT;

ALTER SYSTEM SWITCH LOGFILE;	--Archive online redos
ALTER SYSTEM SWITCH LOGFILE;
ALTER SYSTEM SWITCH LOGFILE;
ALTER SYSTEM SWITCH LOGFILE;

ALTER DATABASE BACKUP CONTROLFILE TO TRACE; SHUTDOWN;         
>
>I'm asking this question because I have never had a convincing answer before
>now
>and because there seems to be a flaw in the logic of the gospel ;-) I would
>really love
>to get a decent debate going on this and *all* contributions are welcome.
>--
>Doug Burns
>
>Certified Oracle DBA
>
>

--

Regards

Matthias Gresz    :-)

GreMa_at_T-online.de

Received on Mon Mar 02 1998 - 00:00:00 CST