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Abstract

A method and means for dynamically managing access by data sets to an LRU disciplined DASD cache staging data sets. A threshold utilizes the inverse of slowly varying global hit ratios (ST) taken over a large number of data sets to control the access by individual data sets in cache as measured by their local hit ratios (DSHR). After an initial trial period, a data set is allowed access to the cache only where DSHR>ST. The method and means are self adjusting in that as I/O demand changes, ST also changes in phase such that an increase in aggregate demand for cache results in elimination of data sets whose DSHRs were marginally equal to the old ST and now less than the new ST. Utilization of a DASD Fast Write and non-volatile store (NVS) can be managed similarly if coordinated with the cache and maintenance of both a global WRITE threshold (WR), local data set write hit ratio (DSHRW), and invocation of Fast Write only where DSHRW>WT (write threshold).

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First Claim