Hello, for info., you could perhaps check (again?):
- is the Oracle client really well installed on your client computer (at the most simple i.e. - amho - with "no service creation", "runtime mode", "custom mode to choose ODBC", "Oracle Windows interfaces x.x.x.x" checked, so an installed driver that can be used by ODBC then, and is the communication protocol selected as "sql net" (it's fairly one of the simplier, AFAIK)?
- is the file tnsnames.ora in your C:\ora920\network\admin, on your client side (ora920 as an example, depending from your client-side installation path, and your Oracle 's version)?
- is the listening communication server port number correct, as Oracle has registered it within the international organization IANA (I've just checked: 1521 seems correct; I was using a server with port number = 2030, which was the default port number proposed during the installation)?
- have you tested in ODBC connections control panel too (under MS-Windows, there should be a "Test connection" button, beside the ODBC connections), by creating a connection with the simplest options: "read-only connection", "disable MT Server"", and NLS_SORT=BINARY, NLS_NUMERIC_CHARACTERS=',.' if possible (the last two options are stored in registry, but it depends on the Oracle's version, IIRC).
- does the local client driver work? You could run "tnsping ora8.world" in a DOS-cmd (if the data source - created in the ODBC connections control panel, from the good choosen installed ODBC Oracle driver - is called\named 'ora8.world', for example), it should respond 'OK<180 ms>'. The tiny tool "tnsping" also allows you to see on which eventual exotic port your server would have been installed (remember to test without a firewall on the client computer, too)? AFAIK, tnsping is the best tool to know if the driver AND your tnsnames.ora are OK, to communicate with your server, from your client computer!
Last trick: from Oracle 10 onwards, under MS-Windows (8, ...? I don't remember in which context), it was sometimes necessary to assign your Oracle user to the group of users authorised to use the created ODBC entry (in "local security policy strategy" of MS-Windows).
Hopefully it might help.