Q1. Explain Optimal Page Replacement Algorithm.
Ans.It is the best page replacement algorithm which is easy to describe but impossible to implement. At the moment when a page fault occurs, some set of pages is in memory. One of these pages will be referenced onto the very next instruction. Other pages may not be referenced until 10, 100, or perhaps 1000instructions occur. Each pages can be labelled with the number of instructions which will be executed before that page is first referenced.
The optimal page replacement algorithm,also known as Look Forward Technique, simply says that the page with the highest labels should be removed. If one page will not be used for 100 instructions and another page will not be used for 50 instructions, removing the former pushes the page fault that will fetch it back as far as possible into the future.