The PUs that can be activated by CBU come from the available unassigned PUs on the CPC drawer. The maximum number of CBU features that can be ordered  is 30. The number of features that can be activated  is limited by the number of unused PUs on the system. However, the ordering system allows for over-configuration in the order. 

You can order up to 30 CBU features regardless of the current configuration. However, at activation, only the capacity that is installed can be activated. At activation, you can decide to activate only a subset of the CBU features that are ordered for the system. 

Subcapacity makes a difference in the way that the CBU features are completed. On the full-capacity models, the CBU features indicate the amount of extra capacity that is needed. If the amount of necessary CBU capacity is equal to four CPs, the CBU configuration is four CBU CPs. 

The number of CBU CPs must be equal to or greater than the number of CPs in the base configuration. Also, all of the CPs in the CBU configuration must have the same capacity setting. For example, if the base configuration is a two-way D02, providing a CBU configuration of a four-way of the same capacity setting requires two CBU feature codes. 

If the required CBU capacity changes the capacity setting of the CPs, going from model capacity identifier D02 to a CBU configuration of a four-way E04 requires four CBU feature codes: two to upgrade from a D02 to a E02 and two to upgrade from an E02 to a E04. 

If the capacity setting of the CPs is changed, more CBU features are required, not more physical PUs. Therefore, your CBU contract requires more CBU features when the capacity setting of the CPs is changed. 

CBU can add CPs through LICCC only, and the z14 ZR1 server must have the correct number of processor drawers that are installed to allow the required upgrade. CBU can change the model capacity identifier to a higher value than the base setting, but does not change the system model. The CBU feature cannot decrease  the capacity setting. 

A CBU contract must be in place before the special code that enables this capability can be installed on the system. CBU features can be added to a z14 ZR1 server nondisruptively. For each system enabled for CBU, the authorization to use CBU is available for a 1 - 5-year period. 

The alternative configuration is activated temporarily , and provides more capacity that is greater than the system’s original, permanent configuration. At activation time, determine the capacity that you require for that situation. You can decide to activate only a subset of the capacity that is specified in the CBU contract. 

The base system configuration must have sufficient memory and channels to accommodate the potential requirements of the large CBU target system. Ensure that all required functions and resources are available on the backup systems. These functions include CF LEVELs for coupling facility partitions, memory, and cryptographic functions, and connectivity capabilities. 

