For all my sins (and because our real DBA is on vacations) this task landed on my laps last week - and since then I started to truly appreciate the work of honest-to-god administrators, non semi-architects/semi-developers like me.
OK, I will stop ranting... A couple of useful remarks:
- Arup/Sam/Darl, I owe you at least one round of good drinks! Your book "RMAN Recipes for Oracle Database 11G" helped me a lot!
- As usual, around midnight I've hit an brick wall. RMAN was complaining about a space "somewhere", I've spent another hour trying to figure what it was about. And eventually I discovered the solution in the bug-list (#8631293):
* RMAN Duplicate command signals RMAN-06561 (available space must be larger than NNN kb) when the recovery area parameter is set.
* The workaround is not to set db_recovery_file_dest and db_recovery_file_dest_size parameters in the init.ora