Ax 2009: Debugging of batch jobs

http://msdn.microsoft.com/en-us/library/cc588679(v=ax.50).aspx

Ax 2012: Debugging of server/batch jobs

All batch jobs and service operations now run in managed code (IL) and require different debugging steps.  Rather than setting breakpoints within X++, you need to set them within the IL code that corresponds to the X++ code and debug in Visual Studio.

1. Open Visual Studio as 'administrator' and attach the debugger to the Ax32Serv.exe process.

1. Once done, open up the file you want to debug in Visual Studio. All of the X++ code is compiled into IL and can be found in the following directory after deployment:..\Program Files\Microsoft Dynamics Ax\6.0\Server\AxaptaDev\Bin\XppIL\source\
2. Set a breakpoint in the file you opened.
3. Go to Ax and run the process in batch mode, or execute the service operation. This will end up hitting your breakpoint, provided you set it in the right place.

If you make some changes to X++ code and want those changes reflected in the generated IL code, you need to do the following AFTER you have compiled the X++ code.Once done, your changes will be reflected in your next debugging session.

Source: https://community.dynamics.com/ax/b/mafsarkhan/archive/2011/05/30/how-to-debug-batch-jobs-and-service-operations-in-dynamics-ax-2012.aspx#.UjwULcZT6k8