Access to computer system resources is regulated by computing an estimated execution time for an operation which seeks to use the resources. Once computed, the estimated execution time is used to make decisions about granting the operation access to the computer system resources. Operations which have an estimated execution time greater than a user-supplied maximum estimated execution time allowable for the operation are denied access to the computer system resources. Operations which are denied access are rescheduled for later operation, queued, or aborted.