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## 9.2 Coupling connectivity options on z15 

A Parallel Sysplex (sysplex) is a collection of z/OS systems that cooperate, using certain hardware and software products, to process workloads. The hardware and software components that make up a sysplex cooperate to provide higher availability, coordinated systems management, and improved growth potential over a conventional computer system of comparable processing power. 

The Server Time Protocol (STP) facility (FC# 1021) is required to synchronize the time-of-day (TOD) clocks for systems in a sysplex that run on different CPCs. 

You can find more details about STP configuration in Chapter 8, “Preparing for Sysplex and configuring Server Time Protocol” on page 163. 

A coupling facility (CF) enables parallel processing and improved data sharing for authorized programs running in the sysplex. The cross-system extended services (XES) component of z/OS enables applications and subsystems to take advantage of the coupling facility. 

In a Parallel Sysplex, the central processor complexes (CPCs) are connected through a coupling facility using coupling links. 

## 9.2.1 Coupling connectivity for Parallel Sysplex on z15 

Coupling connectivity for Parallel Sysplex on z15 use Coupling Express Long Reach (CE LR) and Integrated Coupling Adapter Short Reach (ICA SR). The ICA SR feature is designed to support distances of up to 150 m. The CE LR feature supports distances up to 10km unrepeated between systems, and up to 100km with a qualified Dense Wavelength Division Multiplexer (DWDM). The available options for coupling links on z15 are shown in Figure 9-1 on page 207 

<img src='content_image/989806.jpg'>

Note: z15 is the first high-end machine that does not support InfiniBand coupling links. Like z14 ZR1, only ICA SR and CE LR external coupling links are supported 

