For all of you working with Informix in combination with IBM Websphere, the following IBM RedPaper might be interesting and helpful. It covers the definition of data sources and contains a good description for performing those tasks in Websphere with IBM Informix as database backend:

When an application or WebSphere® component requires access to a database, 
that database must be defined to WebSphere as a data source. Two basic 
definitions are required. First, a JDBC™ provider definition defines an