This paper presents a simulation study of a video-on-demand system. The focus of the study is the effectiveness of different caching strategies on a video-on-demand system with two levels of cache, RAM and disks, in front of a tape library. Using an event-driven simulator, I show that caching was helpful in increasing the service capacity of the system. On-demand caching showed its advantages especially when the requests were clustered around a few popular titles (in other words, there was temporal locality).