1. The fraction of references to one level of the memory hierarchy that must otherwise be fulfilled in the less accessible levels within the hierarchy. Thus for a cache memory the hit rate is the fraction of references that do not result in access to main memory. For a page the hit rate is the fraction of references that do not result in a page turn.

2. The proportion of records or blocks on a file that are retrieved or updated in a batch run or in a given period of time.