System Assist Processors - IBM z13s Technical Manual

zIIPs are orderable by using FC 1927. Up to two zIIP can be ordered for each CP or marked
CP configured in the system.
PUs characterized as zIIPs within a configuration are grouped into the zIIP pool. This
configuration allows zIIPs to have their own processing weights, independent of the weight of
parent CPs. The zIIP pool can be seen on the hardware console.
The number of permanent zIIPs plus temporary zIIPs cannot exceed twice the number of
purchased CPs plus temporary CPs. Also, the number of temporary zIIPs cannot exceed the
number of permanent zIIPs.
zIIPs and logical partition definitions
zIIPs are either dedicated or shared depending on whether they are part of an LPAR with
dedicated or shared CPs. In an LPAR, at least one CP must be defined before zIIPs for that
partition can be defined. The number of zIIPs that are available in the system is the number of
zIIPs that can be defined to an LPAR.
Logical partition: In a logical partition, as many zIIPs as are available can be defined
together with at least one CP.

3.5.6 System assist processors

A system assist processor (SAP) is a PU that runs the channel subsystem LIC to control I/O
operations. All SAPs run I/O operations for all LPARs. All models have standard SAPs
configured. The number of standard SAPs depends on the z13s model, as shown in
Table 3-2.
Table 3-2 SAPs per model
Model
Standard SAPs
SAP configuration
A standard SAP configuration provides a well-balanced system for most environments.
However, some application environments have high I/O rates, which are typically various
Transaction Processing Facility (TPF) environments. In this case, more SAPs can be ordered.
Assignment of more SAPs can increase the capability of the channel subsystem to run I/O
operations. In z13s systems, the number of SAPs can be greater than the number of CPs.
However, additional SAPs plus standard SAPs cannot exceed 6.
Optional additional orderable SAPs
The ability to order more SAPs is an option that is available on all models (FC 1926). These
additional SAPs increase the capacity of the channel subsystem to run I/O operation, which is
suggested for TPF environments. The maximum number of optional additional orderable
SAPs depends on the configuration and the number of available uncharacterized PUs. The
number of SAPs is listed in Table 3-3.
Table 3-3 Optional SAPs per model
Model
Optional SAPs
N10
2
N10
0 - 2
Chapter 3. Central processor complex system design
N20
3
N20
0 - 3
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