A QOS control is one of the most important factors in continuous media applications. The QOS levels of the applications should be maintained even if several contin- uous media applications are running concurrently. Also, the QOS levels should be changed according to a number of applications and their respective importances when a system is overloaded. This paper presents our experience with a video-on-demand system that supports a dynamic QOS control scheme on Real-Time Mach, and shows the necessity of a real-time resource management for building such applications.