Like the DSN-less configuration, ODBC-combined keeps server properties in freetds.conf. The difference is that your applications can refer to the server by its DSN. To make that possible, the DSN entry in odbc.ini refers to the servername entry in freetds.conf.
Example 4.6. Sample ODBC-combined freetds.conf file
; ; freetds.conf ; [JDBC] host = jdbc.sybase.com port = 4444 tds version = 5.0
With this arrangement, an application can connect to the server in two ways, via its DSN (JDBCdsn), or its servername (JDBC).