What is the value returned by Page Life Expectancy, precisely?

The use of the word "will" in this documentation

Indicates the number of seconds a page will stay in the buffer pool without references.

suggests that the PLE value is a prediction of some kind. Is the prediction based on the actual computed average of the length of time pages now in the buffer pool have been in the buffer pool?

Is the algorithm used for computing PLE available?

1 Answer 1


PLE is a measure of how long (in seconds), pages are staying in memory. It is more a measure of the age of the current pages, than a prediction. But if the current load stays the same you should expect the PLE to stay the same.

In reality, it changes, the value grows every second, until there is a big flush then it shrinks.


  • Sorry for the delayed acceptance. Changed computers and browsers and SO lost track of me, no notifications. Probably something I neglected to change.
    – Tim
    Commented Oct 8, 2021 at 13:42

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