Experience contributes important knowledge in many procedures. From the experience gained in tuning the Multiple Virtual Storage (MVS) operating system, a set of guidelines to help MVS installations avoid performance problems are suggested, along with an approach to tuning an MVS system. The guidelines can help a performance analyst isolate the cause of a performance problem. Not all possible problems that might be encountered are included. It is found that most MVS performance problems are a result of poor workload management and are often related to I/O activities.