You need to enable debugging on the server before you can debug your Web Dynpro application. You can enable debugging from within the SAP NetWeaver Developer Studio.
The Java Engine is running and you have specified where it is installed (Window → Preferences →J2EE Engine).
1. Choose Window → Show View → Other.
2. Choose J2EE → J2EE Engine.
3. Choose OK.
4. In the J2EE Engine view, expand the tree and select the relevant process.
You might have to choose Refresh tree to see it.
5. Call up the context menu of the process and choose Enable debugging of process.
The process will restart. This may take some time.
6. Choose Refresh tree to see new status.
If the process has restarted, Debug Mode is now ON.