For a job step, the difference between this event and Event-step-ready is that this event occurs in the child process giving the user exit the opportunity to do things on behalf of the program about to be invoked. For example, if you need to load special modules that the program will be using, this would be the time to do it. This event does not permit you to change data such as program name, whereas Event-step-ready does.
The purpose of this event is to allow your user exit to perform any processing (such a loading of programs to avoid name conflicts or for other reasons) before the program is invoked.
This event and Event-after-PGM-call occur in the child process. All other events occur in the parent process. Your exit cannot remember any events that occurred in the parent process.
This event is currently not implemented.