1. A method for managing mainframe computer system usage comprising: receiving a first performance optimization goal for workload performance in a first service class, the first service class having a first defined performance goal; assessing achievement of the first performance optimization goal; determining whether a logical partition including the first service class is experiencing a processing capacity shortage; receiving a workload criticality designation for the first service class; receiving an automatic change authorization; and if overachievement of the first performance optimization goal is identified, a processing capacity shortage is determined to exist for the logical partition executing the first service class, the workload designation is indicated to be critical, and automatic changes are authorized, then: determining a first preferred value for the first defined performance goal; automatically changing the first defined performance goal to match the first preferred value; and generating a first notification including the first preferred value.