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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 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. 

LPAR:  In an LPAR, 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. z14 is the first IBM Z server to enable SMT for SAPs. All models feature standard SAPs configured. The number of standard SAPs depends on the z14 model, as listed in Table 3-2. 

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## SAP configuration 

A standard SAP configuration provides a well-balanced system for most environments. 

However, some application environments have high I/O rates, typically Transaction Processing Facility (TPF) environments. In this case, more SAPs can be ordered. Assigning of more SAPs can increase the capability of the channel subsystem to run I/O operations. In z14 systems, the number of SAPs can be greater than the number of CPs. However, more SAPs plus standard SAPs cannot exceed 128. 

## Optional other orderable SAPs 

The option to order more SAPs is available on all models (FC #1935). These extra SAPs increase the capacity of the channel subsystem to run I/O operation, which is suggested for TPF environments. The maximum number of optional extra orderable SAPs depends on the configuration and the number of available uncharacterized PUs. The number of SAPs is listed in Table 3-3. 

<img src='content_image/1004531.jpg'>

## 3.5.7 Reserved processors 

Reserved processors  are defined by the PR/SM to allow for a nondisruptive capacity upgrade. Reserved processors are similar to spare logical processors, and can be shared or dedicated. Reserved CPs can be defined to an LPAR dynamically to allow for nondisruptive image upgrades. 

