Connection failure
The connection and/or login can be rejected for any number of reasons including an invalid ODBC installation, an invalid database client, or simply an incorrect password. In any event an error is returned from either ODBC, the database client or the database providing the reason for the connection failure. Unfortunately, in some cases, these errors can be misleading or irrelevant. In such a case the best procedure is to work through the various components.
1 Try and establish a connection to the database using the database vendors tool set. (e.g. sql*plus for Oracle).
2 Check the network access to the database. (e.g. tnsping for Oracle).
3 If the database vendor has supplied tools for accessing the database through its client software, then test the connection with these tools.