Some common reasons that setup/connection issues occur are:
The library path environment variable is not set correctly. Before you can use the driver, you must set the PATH environment variable to the path of the jvm.dll file of your Java Virtual Machine (JVM). For Windows platforms, the library path environment variable is PATH.
The database and/or listener are not started.
The ODBC driver’s connection options are not set correctly when configuring the driver. For example, the host name or port number are not correctly configured. See "Configuring a Data Source" for a list of connection options that are required for the driver to connect properly to the underlying database.