There is a difference of opinion on what is a "better" approach -- having multiple separated catalogs or having a fewer number of catalogs, maybe separated just by function or the version. Both sides are using the same reasons for cons and pros, and I'd like to hear your opinion and reasons for doing this one way versus the other.
That being said, the only time I have implemented two RCs is to have a RC of my main backup RC. For instance, all of my databases use a RC in a database called RMAN_RC. Every time I use RMAN to back up a database, it connects to the RC in the RMAN_RC database. But I cannot use this RC when backing up the RMAN_RC database itself. So I will sometimes create another RC in another database. This way, if I lose one RC, the information to restore it is in another RC. I hope that makes sense.
This was first published in August 2008