After you have established that the database client software and data source are communicating properly (if applicable), the next step in isolating connection problems is to test the ODBC connection to the data source databases.
On Windows systems, use ODBC Administrator to test connections to the data source databases. On UNIX, manually inspect the ODBC configuration files using ivtestlib (for 32-bit) or ddtestlib (for 64-bit) provided in the appropriate ODBC directory under common. You can also use third-party utilities included with your data source.
On UNIX systems, the most likely causes for problems in the ODBC component are that the environment variables for ODBC are not set up or that the odbc.ini file is not configured properly.
ODBC tracing can also be used to track down connection problems. See Using ODBC Tracing.