Tutorials, manuals, documentation for using SAP JCo 3.x
Go to http://service.sap.com/connectors (You'll need an SAP service market place account), click on "SAP Java Connector" > Tools and Services in the left hand navigation tree. You can download the JCO release 3.0.x from there and also download the SAP JCO 3.0 documentation as a PDF file.