Understanding database 3 : Buffer algorithms As we use buffers to boost up our performance, it is also necessary for us to choose a suitable algorithm for our buffer to follow. With formal expression, the ‘ access pattern ’ is the key of ensuring the number of I/Os to be controlled, which has a massive impact on the performance of execution. We introduce the formula for read efficiency here, noted as (number of page requests - physical I/Os) /(number of page requests) And we should also aim for above 0 .8 or 80% for an adequate efficiency. We have 4 basic policies to decide for replacing frames within a buffer, including First in first out (FIFO) ->oldest leaves Least recently used (LRU) <--------------------------- most common ->frame with oldest access leaves Most recently used (MRU) ->frame with freshest access leaves Least frequently used (LFU) ->frame with least access count leaves Most database management systems wo