IBM System Recovery Boost planning considerations

System Recovery Boost can provide additional processing capacity during the limited-duration startup and shutdown "boost periods" in a variety of different ways, depending on the system configuration and on specific operating system exploitation capabilities. On subcapacity machine models (4xx, 5xx, 6xx, and Axx-Yxx), System Recovery Boost can temporarily boost the processing capacity of general purpose processors to run as if they were full-capacity processors, only in those system images that are actively experiencing a boost. This temporary increase in general purpose processing capacity for the boosting images is not visible for pricing purposes, so it does not lead to IBM software licensing cost increases. On servers with zIIP processors, System Recovery Boost is designed to help unlock the parallelism, capacity and acceleration potential of those zIIP processors by temporarily allowing general-purpose workload to run on them during the boost period, only in the system images that are actively experiencing a boost. This use of zIIP processor capacity applies only to operating systems that support zIIPs (for example, z/OS), and to system images that actually have zIIP processing capacity defined to them.

System Recovery Boost requires operating system exploitation. z/OS will fully support the boosting of general purpose processors on subcapacity machine models to run as if they were full-capacity processors and also the use of zIIP processors to run general purpose work during boost periods. z/OS will support such boosts during a planned system shutdown and during system startup. The zIIP Boost can improve z/OS recovery time by making CP-only work eligible to run on zIIPs and CPs during the boost period. In order to exploit this capability, the logical partition must use shared processors, run with HiperDispatch=Yes, and have one or more logical zIIPs defined. Typically, you would define as many initial zIIPs as you need for normal operation. However, you may want to consider increasing the number of reserved logical zIIPs you have defined for the logical partition. These additional reserved logical zIIPs, up to what can be backed by physical zIIPs at the time, are automatically configured online by z/OS during the boost period for the logical partition. z/OS automatically configures these same logical zIIP processors offline at the end of the boost period. Stand-Alone Dump (SADMP) will support boosting of general purpose processors on subcapacity machine models only to provide additional processor capacity for use in capturing diagnostic information for system failures. z/VM and z/TPF will provide support for boosting of general purpose processors on subcapacity machine models only for both planned system shutdown and system startup. In the case of z/VM, the increased capacity of general purpose processors during a z/VM system startup or shutdown can be "inherited" by some second-level guests to provide additional processing capacity to accelerate the guest startup and/or shutdown processing. The z/VM running on IFL processors will not experience any capacity boost for IFLs.