Significance of ".WORLD" on end of Oracle connection
.WORLD is a type of domain. You need it in tnsnames.ora if this is configured in your sqlnet.ora file (names.default_domain parameter). If this is not present in sqlnet.ora and you have it in tnsnames.ora, you have to append it manually. Sqlnet.ora


  The value of this parameter is appended to the net service name if the net service name doesn't already have a domain.


The .WORLD isn't needed at all if names.default_domain isn't set. In order to get the client working, just make sure the tnsnames.ora file on the server (in the network/admin folder) matches the tnsnames.ora file on the client (in the client network/admin folder).