Instead of strugling further follow the steps.

1.Alter database rename global_names to xxx
on both the servers.
2.create database link abcd.xxx connect to user_name identified by password using
'(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = your host )(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = database_sid)
)
)';