Oracle Message RMAN-06740 - database name is not specified

ERRORdatabase name is not specified
CAUSEThe command failed because of the following: o RMAN is not connected to the target database o The database name is not specified in the command o DBID is not set with the SET DBID command
ACTIONAny one of the following actions will fix the problem: o Connect to the target database o Specify database name o Set DBID with SET DBID command