what is sequential flooding?

Question

This might be simple, but I can't get my head around it. Can anyone give me an example of sequential flooding? In the textbook I am reading and in Internet sources it is stated

When the number of buffer frames is less than the pages in file, this will result in reading every page of the file. This is a nasty situation caused by LRU and repeated scans when

# frames < # pages in file.

Using LRU, every scan of the file will result in reading every page of the file."

But what exactly is it? Why does it happen?

Anschluss

Answer 1

Let us say there is 2 buffer frames Frame #1 and Frame #2, 3 pages in file P1, P2 and P3. What would happen if we scan the file twice(P1, P2, P3, P1, P2, P3) with sequential scan?

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As you can see, using LRU, every scan of a page will cost a page miss. However, MRU will do much better.

Whimsey