WHAT IS BELADY'S ANOMALY? IN WHICH REPLACEMENT ALGORITHM IT HAPPEN?
BELADY'S ANOMALY : It is a problem which occur when we increase the number of frames . by increasing number of frames , number of page fault also increases. It happens in FIFO page replacement algorithm. In FIFO when we increase the number of frames we are giving more memory to processes . So Page Fault should decrease but here the page fault are increased . This problem is known as BELADY'S ANOMALY.
More frames= More page fault
For example : Find the Page Fault for the pages 3,2,1,0,3,2,4,3,2,1,0,4 for number of Frames a) 3frames , b)4 frames .
Using 3 frames , (fig -I )Here number of frames is 3 and Page Fault =9
Using 4 Frames , (fig-II) Here number of Frames =4 and Page Fault =10
As we see the above example if number of Frames increases , number of Page Fault also increases. they are directly proportional with each other and inversely proportional to page hit.