I've been trying for the last few days to connect to a DB2 database from WebSphere 3.5 (on Redhat) using the extended JDBC 2.0 API. Finally I got an answer from someone on a newsgroup, but I thought I'd also post it here because it looks like a lot of people run in to this. I was getting a ClassNotFoundException: COM.ibm.db2.jdbc.app.DB2Driver (or also COM.ibm.db2.jdbc.DB2XADataSource if JTA is turned on) when trying to use the connectiong pooling via JNDI. Besides doing usejdbc2 and having all the environment variables setup correctly, you also need to edit the $WAS_HOME/bin/admin.config file and add the /java12/db2java.zip file to the admin's classpath. For me this made everything magically start working.