Hot Backups

[Keely Jackson]

I need to do a 'hot' backup of an oracle database. The DBA's inform that it is not feasible in the circumstances to use the hot-backup mode. Does anyone know of any product that would allow me to produce a 'clone' or 'snapshot' of the files that I can then backup. The system does not use mirrors so unfortunately I cannot split the mirrors, back up and re-merge which would have been ideal.

Cheers
Keely

[ian Dennison]

What are the circumstances that the DBAs are quoting? Do you have the Oracle Backup and Recovery manual handy?

In order to perform a Hot (or Online) Backup of Oracle, it must be in Redo Log Mode. If it is not, the options are severely limited for the types of backup to perform.

The quickest (and dirtiest) method would be to create a separate data area on disk, and perform either an Oracle 'export' or a 'cp' of the relevant files (Datafiles, Control Files, Online Redo Logs) while the Database is down.
Then start the DB up again and perform Backups of the Files that have been copied / exported.

Are the DBAs averse to using Incremental Backups during the week, and Full Backups on the weekend? How much data are we talking about here?

Share and Enjoy! Ian

[James R. Ferguson]

Hi Keely:

I think I'd start by asking the DBA if he/she knows how to setup and handle hot-backups in the first place, or is that the aversion?

As for snapshots of filesystems, Online JFS supports this method of backup.

Regards!

...JRF...

[Peter Kloetgen]

Hi Keely,

there is a product which is able to do your job, the name is Omniback II4.1. The vendor is HP, you can find a lot of information on these sites. Omniback has a Oracle Integration Agent which you have to install on the computer running the database. Then Ominback works with snapshots of the files and offers also the possibility to backup open files later, when they are no longer in use. You have to pay for Omniback, it works on HP and or NT/2000 as platform for the Cell Manager, Clients are available for allmost every UNIX derivate, Novell, Linux, some Mainframes and so on.

Allways stay on the bright side of life!

Peter

[Stefan Farrelly]

Get a 90 day trial copy of HP's Omniback backup software - this interfaces to Oracle (via RMAN) and does hot online backups so you dont need to shutdown the database. We use them -works great.

[Keely Jackson]

Perhaps I need to re-phrsase my question. Apologies if I have confused you all.

We also run tru-64 boxes here. With their equivalent of lvm (advfs) you can produce a 'clone' copy of a logical volume. Is there any product around that can do anything similar for hp-ux (apart from splitting mirrors).

The database's are run in archive-redo log mode. Apparently we could do a hot-backup of each db file in sequence but then you get problems of re-syncronising when you restore or we could put the db into hot-backup mode, copy all the files but this would take to long and the temp area required to hold the changes would be quite large. We have inherited Omniback - but don't know much about it - so I will also look into using that. Thanks.

[ian Dennison]

Keely,

Any Applications running on top of Oracle?

Online Backups are only really good for recovering partial loss of the Database Files. If you lose the entire Database, or one of the System Datafiles, you need to perform a recovery of the Database from an Offline Backup (complete with Control Files and Online Redo Logs), then roll forward with Archived Redo Logs to the point of recovery.

I would recommend putting the entire database in Backup Mode at the same time. This will have the effect of causing more Redo Logs being reproduced, but will mean that the SCN on all the Datafiles will be the same. OmniBack is pretty whizz-bang when integrating with Oracle; I have always found it very reliable.

Share and Enjoy! Ian

[Tilok]

hi Keely Jackson,
RMAN (oracle backup utility) can take the database backup online if the database is in archive mode, and also u can fire backup simultaneously for all ur live database. If the database is large and daily transacation are high, than u can ask DBA team to define BACKUP policy to implement incremental and cumulative backup of database, as RMAN supports same.

Regards
tilok

[John Palmer · Accepted solution]

Hi,

The HP equivalent of your tru-64 clone is the filesystem snapshot that Jim Ferguson mentioned above. This is part of Online JFS though which is a chargeable option.

It's not true that you need to have an offline backup in order to perform a complete recovery of a database or loss of a system datafile. You can do it from a hot backup providing you have the relevant archived redo logs.

The big difference between hot (online) and cold (offline) Oracle backups is that in order to restore from a hot backup, you always have to do database recovery.

Regards,
John

[A. Clay Stephenson]

Hi Keely:

I do backups like this daily. In my case I use the OnlineJFS vxfs snapof mount. They work just like the ones you are used to in Digital Unix. In my case, hotbackups were useless because I have meta-data on other servers that describes the Oracle data. If one is backed up at 12:00 and the Oracle at 12:01, both are essentially worthless. My solution was to shutdown the apps and database, snapof mount the filesystems, and then bring everything back up. For less than 2 minutes of downtime per day, I have all the safety of a cold backup with almost all the convenience of a hotbackup.

Regards, Clay

[Keely Jackson]

Thanks or all your comments.

We have both online JFS and Omniback so I guess I can sort something out.