Before you can debug your message flow, you must attach the flow debugger to the integration server where your flow is deployed, then start a debugging session.
From the IBM App Connect Enterprise Toolkit, you can attach the flow debugger to multiple integration servers that are running on the same or on different host computers, and debug their flows (and therefore multiple messages) simultaneously.
An integration server can be debugged by only one user at a time. If you attach your debugger to an integration server, another user cannot attach a debugger to that same integration server until you have ended your debugging session.
To attach the debugger to an integration server:
Send a message through your message flow.