Thin Interrupt support is available since zEC12/zBC12, and proved to be efficient and performant in numerous different test and customer shared-engine coupling facility configurations. 

For CFCC running on z15, DYNDISP=THIN is now the default mode of operation for coupling facility images that use shared processors. 

## 3.5.5 IBM Z Integrated Information Processor (FC 1947) 

A zIIP$^{5}$ reduces the standard processor (CP) capacity requirements for z/OS Java, XML system services applications, and a portion of work of z/OS Communications Server and Db2 UDB for z/OS Version 8 or later, which frees up capacity for other workload requirements. 

A zIIP enables eligible z/OS workloads to have a portion of them directed for execution to a processor that is characterized as a zIIP. The zIIPs do not increase the MSU value of the processor and so do not affect the IBM software license changes. 

z15 is the third generation of IBM Z processors to support SMT. z15 servers implement two threads per core on IFLs and zIIPs. SMT must be enabled at the LPAR level and supported by the z/OS operating system. SMT was enhanced for z15 and it is enabled for SAPs by default (no customer intervention required). 

New with z/OS 2.4, the z/OS Container Extensions$^{6}$ allows deployment of Linux on Z software components, such as Docker Containers in a z/OS system, in direct support of z/OS workloads without requiring a separately provisioned Linux server, while maintaining overall solution operational control within z/OS and with z/OS qualities of service. Workload deployed in z/OS Container Extensions is zIIP eligible. 

## How zIIPs work 

zIIPs are designed for supporting designated z/OS workloads. One of the workloads is Java code execution. When Java code must be run (for example, under control of IBM WebSphere), the z/OS JVM calls the function of the zIIP. The z/OS dispatcher then suspends the JVM task on the CP that it is running on and dispatches it on an available zIIP. After the Java application code execution is finished, z/OS redispatches the JVM task on an available CP. After this process occurs, normal processing is resumed. 

This process reduces the CP time that is needed to run Java WebSphere applications, which frees that capacity for other workloads. 

