Cause
You do not have a static listener entry for the instance you are attempting too connect to. This uses instance automatic registration. The instance registers with the listener when you mount and PMON is started. Before there is nothing to register the database to the listerner so the instance is blocked.
RMAN requires a static listener entry and the tnsnames.ora should not contain FAIL_OVER=ON or LOAD_BALANCING. Just a plain vanilla dedicated server connection.
Fix
1. Create a static entry for the SID to the SID_LIST in the listener.ora
OR
2. Use the Oracle10G feature :
tnsnames.ora
....
CONNECT_DATA=((SID=....) (UR=A))
This fix is required for administrative connections where we specify (UR=A)
in connect data.
