If the response to an SDC event is "machine already in use" that means that DFWorks thinks the "machine" is running a job already and it won't let SDC commands for a different job or process step be entered until the first one is completed. There are some ways to avoid getting into this state in the first place:
If you do get the "machine already in use" error, the procedure below will stop the job on that machine most of the time. I was able to use it today to recover all 3 machines IAEXC23, IAEXC2, and IAEXC28:
The QCStop and PrepStop commands are new, I just enrolled them today via Admin Enrollment/Mailrun Management/Scan Event Enrollment. You may want to create the same commands on the Ohio system in case they are needed there.
There's no easy way to tell which command (QCStop, PrepStop InsertStop, SortArrivalStop, or SortStop) is needed to stop the machine. It depends on what process step DFWorks thinks the machine is executing. This information is not displayed on the Home Page. However, if each machine is used for only one process step then use the appropriate command for that process step. (Use QCStop for a PrintQC machine, PrepStop for an InsertPrep machine, etc.). If you aren't sure which process step it is, it's OK to try all of the commands to see if any one will work, the worst thing that will happen is you will get another "machine already in use" error.
UPDATED: April 19, 2017