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## Buffer Pool LRU Algorithm 

The buffer pool is managed as a list using a variation of the LRU algorithm. When room is needed to add a new page to the buffer pool, the least recently used page is evicted and a new page is added to the middle of the list. This midpoint insertion strategy treats the list as two sublists: 

•At the head, a sublist of new (“young” ) pages that were accessed recently 

•At the tail, a sublist of old pages that were accessed less recently 

<img src='content_image/848472.jpg'>

The algorithm keeps frequently used pages in the new sublist. The old sublist contains less frequently used pages; these pages are candidates for eviction. 

