If we increase our degree of multiprogramming, we are over allocating memory. If we run six processes, each of which is 10 pages in size, but actually uses only five pages, we have higher CPU utilization and throughput, with 10 frames to spare. It is possible, however, that each of these processes, for a particular data set, may suddenly try to use all 10 of its pages, resulting in a need for 60 frames, when only 40 are available. Although this situation may be unlikely, it becomes much more likely as we increase the multiprogramming level, so that the average memory usage is close to the available physical memory. (In our example, why stop at a multiprogramming level of six, when we can move to a level of seven or eight?)