Re: Backup planning experience

"Andreas Schlager" <aschlager_at_eunet.at> wrote in message news:imBg6.169$Q3.3177_at_nreader1.kpnqwest.net...
> alexberi_at_my-deja.com wrote in <95tuch$df3$1_at_nnrp1.deja.com>:
>
> >
> >-Is it a good idea to backup the whole database incrementaly or to
> >treat the table separatelly?
> >-What about the partitions?
> >-If the database can be shutdown during the night do I need to backup
> >archive logs?
> >-the output device is a tape, do I need a different tape for each daily
> >backup?
>
> Hi Alex,
>
> I don't know RMAN in detail.
> if you want to keep the database running 7x24, you have to set the db in
> backup-mode (alter database begin backup or somehow),

Close, but no banana. The command is alter TABLESPACE x begin backup. And having issued that for a tablespace, you can then copy the relevant datafiles *for that tablespace only*, and then issue the alter tablespace x end backup command. Then you move onto the next tablespace.

>backup ALL DB-Files,
> then alter database end backup, and now all archives generated during
> backup until now.
>
> If you shut down your DB and if you backup ALL db-files (incl. redo logs,
> contr. files), you should not need the archives (someone please correct me
> if I'm wrong here).
>

You are wrong here. If you are in archivelog mode, you should ALWAYS backup your archives, since they are the only thing allowing complete recovery of all data after a media failure. Oracle hasn't introduced 5-way writing of archives in 8i just for fun, you know! If the database is shutdown for backup, it is permissible to take backups of your online redo logs, whether you are in archivelog mode or not. If you are doing hot backups, it is very, very foolish to copy your online redo logs (the copies will be internally inconsistent and utterly useless for recovery purposes).

> I'm sure, you would need more than one tape - I'm sure you need a tape
> library to backup 200 gigs. No chance at all to do it without. And use
> *fast* tapes! Keep in mind, that in the case of disaster you need at
> minimum the time to restore that it took to backup the data.
>

And for that reason, my strong advice is to acquire the hard disk capacity to backup onto disk first, and to take the tape backup from that copy.

> If you plan to use incremental backups, also think about the time factor.
> First, you have to restore a COMPLETE offline backup, then you have to
> apply ALL following archives!!!

Not true. If he's taking incremental backups, he must therefore be in archivelog mode (otherwise he *has* to perform closed, whole database backups). In archivelog mode, if one datafile bites the dust, it is perfectly legitimate to restore the one problem datafile and apply the redo from that point on, for that one file (hence the 'recover datafile x' command).

>This could take a couple of days, if you
> have to apply a lot of archives!
>
> I hope, that helps a little bit.
>
> If I'm wrong somewhere here, please correct me, group!
>

I think the two of you could both do with a swift trip to http://www.geocities.com/hjroz2000/backup_and_recovery.htm

There's a document there that may be of some help in understanding the principles (and some RMAN examples).

Regards
HJR
> Andy.
Received on Thu Feb 08 2001 - 16:30:36 CST