[oracle@hostname ~]$ emctl status dbconsole
Environment variable ORACLE_UNQNAME not defined. Please set ORACLE_UNQNAME to database unique name.
SQL> SELECT name, db_unique_name FROM v$database;
NAME DB_UNIQUE_NAME
--------------------------- ------------------------------------------------------------------------------------------
DB5 db5_db
[oracle@hostname ~]$ export ORACLE_UNQNAME= db5_db