How can be actually debug a BPEL application once we have it running.

The process that I have implemented is a slightly involved one and goes through multiple stages. It works as expected till the first few steps but then gets lost somewhere. I need to close-in on the issue that is causing this problem.

Any tool that can help me simulate would be great!

You can look at the steps of the process in the console, and see where it went astray.

Thanks,

Antoine

As Antoine says, you can review each event from the BPEL engine for a single instance of a process. That is run your process, then select the instance from the BPMS-console and look at the events which are tied to the BPEL line numbers. These events are documented in the Apache ODE site ... as is a means to filter them.
This is all a bit low level if you are thinking of your process in terms of the BPMN diagram. It is a pity you cannot just step through the process diagram and review variables.
I generate a poor man's trace through the process by creating a pool variable and concatenating data from each task (usually just the fact that I have passed this way) into it. A quick look at the variable on failure or during the process is usually enough to tell me where I went wrong.
David

What I was meaning was more about following the process instance in the bpms-console web application. You can see the current path of execution, the state of all the variables and the events David mentions.