You can specify the JDBC driver by doing the following:
On Linux, the start file is:
ProductDir/connectors/JDBC/start_JDBC.sh
On Windows, the start file is:
ProductDir\connectors\JDBC\start_JDBC.bat
On i5/OS, the start file is:
ProductDir/QIBM/UserData/WBIServer44/QWBIDFT/connectors/JDBC/sart_JDBC.sh