IBM z13s Technical Manual page 146

Removal of an option for the way shared logical processors are managed under
PR/SM LPAR: IBM z13 and z13s servers will be the last z Systems servers to support
selection of the option to "Do not end the time slice if a partition enters a wait state" when
the option to set a processor runtime value has been previously selected in the CPC
RESET profile. The CPC RESET profile applies to all shared logical partitions on the
system, and is not selectable by logical partition.
All statements regarding IBM plans, directions, and intent are subject to change or
withdrawal without notice. Any reliance on these statements of general direction is at the
relying party's sole risk and will not create liability or obligation for IBM.
HiperDispatch
PR/SM and z/OS work in tandem to use processor resources more efficiently. HiperDispatch
is a function that combines the dispatcher actions and the knowledge that PR/SM has about
the topology of the system.
Performance can be optimized by redispatching units of work to the same processor group,
keeping processes running near their cached instructions and data, and minimizing transfers
of data ownership among processors and CPC drawers.
The nested topology is returned to z/OS by the Store System Information (STSI) instruction.
HiperDispatch uses the information to concentrate logical processors around shared caches
(L3 at PU chip level, and L4 at CPC drawer level), and dynamically optimizes the assignment
of logical processors and units of work.
z/OS dispatcher manages multiple queues, called
eight processors per queue, which fits nicely onto a single PU chip. These queues are used to
assign work to as few logical processors as are needed for an LPAR workload. So, even if the
LPAR is defined with many logical processors, HiperDispatch optimizes this number of
processors to be near the required capacity. The optimal number of processors to be used is
kept within a CPC drawer boundary where possible.
Tip: HiperDispatch is now also supported by z/VM V6.3.
Logical partitions (LPARs)
PR/SM enables the z13s servers to be initialized for a logically partitioned operation,
supporting up to 40 LPARs. Each LPAR can run its own operating system image in any image
mode, independently from the other LPARs.
An LPAR can be added, removed, activated, or deactivated at any time. Changing the number
of LPARs is not disruptive and does not require POR. Certain facilities might not be available
to all operating systems because the facilities might have software corequisites.
Each LPAR has the same resources as a real CPC:
Processors: Called l
They can be dedicated to an LPAR or shared among LPARs. When shared, a processor
weight can be defined to provide the required level of processor resources to an LPAR.
Also, the capping option can be turned on, which prevents an LPAR from acquiring more
than its defined weight, limiting its processor consumption.
LPARs for z/OS can have CP and zIIP logical processors. The two logical processor types
can be defined as either all dedicated or all shared. The zIIP support is available in z/OS.
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ogical processors
, they can be defined as CPs, IFLs, ICFs, or zIIPs.
affinity queues
, with a target number of