Check in advantage.webMethods.com site, in 6.0.1, JDBC adapter user guide PDF. Its strange that u worry about data source class…try to be approachive always…search for information u will find everything unlike other EAI.
The data source class that u have tried with is correct, but I think the script files are not copied properly in the database that will create table spaces for the connection and process of extracting data.
I would suggest you to try configuring the connection again with new databast name in DB2 v8.1.
Hope this will resolve the issue.