Hot Set Algorithm

1. Hot Set : A set of pages over which there is a looping behavior.
2. Hot Point: If a query is given a large enough buffer to hold the hot sets, the number of page faults will be minimum. As the size is decreased, more faults result as the size of buffers becomes less than the hot set. This shows up in the points of discontinuity in the plot of number of page faults as a function of buffer size. The point of discontinuity is the hot point.
3. Each query is provided a separate list of buffers.
4. Buffers in each query domain are managed by LRU.
5. The number of buffers for a query is predicted by the Hot Set Model.
6. A new query is allowed if its hot set size <= available buffer size.
7. Drawbacks
   1. LRU usage lacks a logical justification.
   2. Memory might be over-allocated and hence under-utilized.
   3. There exist reference patterns where LRU performs as well as a scheme with a lower overhead. Hence LRU is unnecessary.