In this algorithm, pages are replaced which would not be used for the longest duration of time in the future. Example-2:Consider the page references 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2, with 4 page frame. Find number of page fault. Initially all slots are empty, so when 7 0 1 2 are allocated to the empty slots —> 4 Page faults 0 is already there so —> 0 Page fault. when 3 came it will take the place of 7 because it is not used for the longest duration of time in the future.—>1 Page fault. 0 is already there so —> 0 Page fault.. 4 will takes place of 1 —> 1 Page Fault. Now for the further page reference string —> 0 Page fault because they are already available in the memory. Optimal page replacement is perfect, but not possible in practice as the operating system cannot know future requests. The use of Optimal Page replacement is to set up a benchmark so that other replacement algorithms can be analyzed against it.
