AVDB =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = TCP)(HOST = <hostname>)(PORT = 1555))
 (CONNECT_DATA =
 (SERVER = DEDICATED)
 (SERVICE_NAME = AVDB)
 )
 )

1. Open the /<ORACLE_HOME>/network/admin) e.g. /u01/app/12.1.0/grid/network/admin/tnsnames.ora file in a text editor.  The tnsnames.ora is a configuration file that defines databases addresses for establishing connections to them.
2. Append the generic top-level domain name (e. g., .COM) to the the SERVICE_NAME value.  For example, change (SERVICE_NAME = AVDB) as follows:

AVDB =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = TCP)(HOST = <hostname>)(PORT = 1555))
 (CONNECT_DATA =
 (SERVER = DEDICATED)
 (SERVICE_NAME = AVDB.COM)
 )
 )

3. Stop ACM:

$ acm stop

4. Connect to the database as sysdba and run the below:

$ sqlplus sys/<password> as sysdba
SQL> ALTER DATABASE RENAME GLOBAL_NAME TO AVDB.COM;
SQL> alter system set db_domain="com" scope=spfile sid='*';
SQL> commit;
SQL> exit

5. Restart the database:

$ acm stoporacle
$ acm startoracle

6. Open the /home/oracle/Aveksa_System.cfg file in a text editor.  
7. Change the value of the ORACLE_SERVICE_NAME from ORACLE_SERVICE_NAME=AVDB to ORACLE_SERVICE_NAME=AVDB.COM, as shown:

ORACLE_SERVICE_NAME=AVDB.COM

8. Start ACM again:

$ acm start