Did you define database pools in your nsd.tcl file? That's the first thing to verify.
Take a look at the logfile AOLserver generates on start up and make sure that the Oracle driver's being loaded. There will be an error message in the log if it's not. That error message will depend on *why* it's not being loaded so I can't give you a specific message to search for. Just look for "Error".
If the driver's loaded and you've defined database pools, make sure your Oracle user name and password are correctly defined in your nsd.tcl file.
