The "C" in DMAIC is for control, and this step, like the others, can be thought of in a heavy way or in a light way, depending on the industry you're in and the focus of your project. The basic intention of control is to make sure the organization commits to institutionalizing the revised process and ensuring its enhanced performance. From this viewpoint, every process program needs a "C" step.
As discussed in Part 1 of this book, corporate habits, routines, and cultures can be hard things to change. When you introduce a new process or adjust an existing one, the company may have a tendency to want to revert back to their old ways. That's understandable. The old ways are usually very familiar, so they are easy to use. They seem natural because "that's the way things have always been done." And, good or bad, they were at least predictable. They were known quantities. But honoring such entropy-driven momentum is not a formula for improvement. And it's certainly not a formula for success.
The action behind control is to support the new way with the kinds of resources needed to make the new way the accepted way. To do this, you want to prevent the organization from reverting back to the old way. You want to set controls into the environment to keep the process on a true course.
A common disappointment in the field of process improvement is lack of control. We have heard stories of organizations that spend money and time to develop a program, and what they produce may end up being ...