Originally posted by hamhey

$ rman target / catalog rman/rman@rcat

Recovery Manager: Release 8.1.5.0.0 - Production

RMAN-06005: connected to target database: RCAT (DBID=268301244)
RMAN-06008: connected to recovery catalog database
It is clear that you are connecting to the Catalog database as your target database. I think i told you to keep the target and the catalog database seperate.

Use $ rman target sys/password@target catalog rman/rman@rcat

after connection do

RMAN> register database;

Clearly mention the target username/password and the connect_string.