Proactive simulation is a new tool, which can be especially useful for driving complex manufacturing facilities. Indeed, the data collected after such simulations can be very useful to be able to take the best decision in the shortest time as the facility is currently running. This paper provides an insight into the different concepts of proactive simulation. Special emphasis is placed on the place of simulation in the control loop, and especially its relationship with the decisional center. The facility supporting this architecture is also briefly presented.