Pardon the Interruption

The community of scheduling practitioners has spoken. And the message is loud and clear. Some activities that need to be worked into a schedule  take longer than one work shift–hey might even take longer than a week! Thus, any scheduling software must be able to accommodate interruptions.

For example:

  • My printing presses shut down at 5:30 each day and then resume operations at 7:30 the next morning.
  • My staff works a normal day shift with weekends and holidays, but their typical work assignments usually take more than eight hours to perform.
  • We use idle times between orders to make stock that goes into inventory.
  • I have a project that can be worked on intermittently, but I don’t want it to override the other things that are already scheduled. I just want to work on the project on-and-off as time permits.

Often when a scheduler–human or computer–looks for times when an activity could be scheduled, they might find several when resources are available, but only for intervals that are too short. For example, a four-hour activity could be started at 3:00 pm, but the crew goes home at 5:30! If that activity is interruptible, the 3:30 start time is the right time to start such an activity. It can be finished the next morning.Downtimes are normal in most organizations. Some activities cannot be interrupted by those downtimes but others can. If your automated scheduling system can’t tell the difference, it will leave holes that should be filled with productive work. Your organization is not working up to its full capacity.

Consider a task that requires Joe to do the set-up, both Joe and Sally working together for a couple of hours, and then Chris to finish the task with a special piece of equipment. The task is interruptible, so it can be stopped temporarily at quitting time and resumed the next morning. The scheduler must recognize that Joe, Sally and Chris will be unavailable over night, and also may have other assignments, including some for the next day. The task requires that Joe and Sally work together during the middle of the task.  It is not easy to see how to interrupt this task for the overnight break and resumed later.  But a good schedule requires this interruptible task to be scheduled properly.

And then what if a change occurs and the task just described is no longer considered interruptible?  Your scheduler should be able to distinguish between the two situations.

Many scheduling systems simplify this problem by scheduling left-to-right–that is, from earlier times to later times. However, when a revision is required, all activities scheduled later than the time of the change must be unscheduled and rescheduled from that point forward. This simplifies the interruptible situation a little, but leads to a very volatile work environment since many activities that didn’t need to be changed may be changed unnecessarily.   Sound familiar?

Interruptible activities must be accommodated in systems that can schedule and reschedule into holes in an existing timeline. Can your software do that?