Well, I thought of two backup strategies like that:

Strategy #1

- Flashcopy database to a backup disk (full); after that, production remains with normal activity

- Configure a clone database on another server, accessing flashcopy backup as its datafiles. Register that "clone" database on RMAN

- Backup the clone database with RMAN directly to tape. Here, we choose full/incremental backups as appropriate. Full export the export database as appropriate.

In case of disaster, we would:

- Restore/recover from RMAN to backup disk;
- Mirror backup disk over production disk;


Strategy #2

- Flashcopy database to a backup disk (full/incremental as appropriate);

- TAR the contents to tape;

In case of disaster, we would:

- Restore the tape contents to disk;
- Apply archivelogs as needed;


#2 seems more simple, but it relies only on hardware and doesn't involve RMAN. #1 takes advantage of RMAN features, but it's more complex and falls on extra licensing (it's almost like Data Guard).

Anyway, we'll be probably working on RAC, which makes the issue more challenging