How to Debug the WebDypro Program

Hi all,

I am a WebDynpro beginner developer. I did some coding recently, and my question is how to debug the Webdynpro program. I find a button in the toolbar, "Set/Delete External Breakpoint". But every time I press it, There is a message occured "User *** is locked" (User *** is my user name in SAP).

Is there some additional setting if I want to use debugging??

Thanks .

Ming