A method to monitor the behavior of a working set cache of a full data set at run time and determine whether it provides a performance benefit is disclosed. An effectiveness metric of the working set cache is tracked over a period of time by efficiently computing the amount of physical memory consumption the cache saves and comparing this to a straightforward measure of its overhead. If the effectiveness metric is determined to be on an ineffective side of a selected threshold amount, the working set cache is disabled. The working set cache can be re-enabled in response to a predetermined event.