Minimizing backup induced downtime

Hello.

As you might have noticed :), I'm trying to learn RMAN and am thinking about how to use it right for our backups. As it seems to me right now, the use of RMAN will make the downtime because of backup *LARGER* than it is right now.

Let me explain how I currently do a backup.

1. Shut down application, which uses Oracle as a backend
2. Shut down Oracle
3. Create filesystem snapshots with ZFS on Solaris 10
4. Start backup to tape of filesystem snapshots. When done, remove snapshots
5. Startup Oracle
6. Startup application

The step 4 is run in the background. Because of this, the actual downtime is very small (a matter of seconds. At most, it's 1 minute). I'm currently shutting down everything, so that the files on backup are in a consistent state.

I'm now thinking about how to fit RMAN into this picture. I think it might look something like this:

1. Shut down application, which uses Oracle as a backend
2. Have RMAN create backup of database
3. Create filesystem snapshots with ZFS on Solaris 10
4. Start backup to tape of filesystem snapshots. When done, remove snapshots
5. Startup application

Here, step 3 is in background. But I cannot start step 3, before step 2 is actually finished. Because of this, the downtime of the application will be larger, won't it? Granted, I don't have to shutdown the application, but then I don't know that I'm in a consistent state. Suppose that I do not shutdown the app while RMAN is running. Then a user comes, adds/deletes/modifies something. This modification is then, of course, not part of the backup I'm doing at this run. Even worse - the FS snapshot doesn't "harmonize" with what's in the DB (the application creates/deletes files in a so called "vault", which is some directory on the server).

Because of all of this, I'd like to shutdown the application while RMAN is running.

In such a scenario/setup, wouldn't RMAN make the downtime larger? Or am I overlooking something completely (which might of course be true)? Hm, right now, I'm pretty much thinking, that a shell script based backup (as I'm currently doing) is a better approach, don't you think?

Regards,

Alexander Skwar Received on Thu Jul 12 2007 - 06:33:56 CDT