Defined capacity is an optional setting that can be changed dynamically. Use the Hardware Management Console (HMC) to establish or change a defined capacity. You can also establish a defined capacity in the LPAR Image Profile, which ensures that the desired defined capacity is used if the system is re-IPLed. The defined capacity setting is in terms of MSUs. In cases where there are different values for hardware MSUs and software pricing MSUs for a given CPC, the defined capacity should be established in terms of software pricing MSUs. If you establish a defined capacity for an LPAR that has a PR/SM hard cap (enforced relative weight) or dedicated CPs, the defined capacity is ignored.

If you establish a defined capacity in an LPAR, z/OS workload management (WLM) monitors the four-hour rolling average utilization of that LPAR. If the four-hour rolling average utilization of the LPAR exceeds the defined capacity, the LPAR is temporarily capped (this is called soft capping) until the four-hour rolling average drops back below the defined capacity. The LPAR four-hour rolling average utilization can exceed the defined capacity. However, if the four-hour rolling average does exceed the defined capacity and soft capping is applied, it is possible (while being soft-capped) for the four-hour rolling average to continue to rise and to exceed the defined capacity. In these cases, SCRT reports the defined capacity value and IBM® charges customers at the defined capacity level rather than based upon the higher four-hour rolling average utilization.