Consider this, you've got no DataGuard at your disposal. Single node, relying on your RMAN-backup on disk, which is fortunately copied to tape. Now your complete node is burning down. What's is left is your RMAN-backup. In a bad scenario you'll have to restore this to another node.
It is considered a skill every DBA should have, cloning / duplicating a database with RMAN. My own basic checklist through an example: Cloning of the DEVDB on the node LARRIE to node ELLISON, new database name DEVDBNEW
A proper backup is the base for a well and relaxed administration of yout databases.What follows is a backup-script which I use for several customers. It's backing up all in the same directory and I tested the restore frequently.