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a. 12x IFB3 protocol supports a maximum of four CHPIDs and connects to the other HCA3-O port. When connected to a HCA2-O port, 12x IFB protocol is used. The protocol is auto-configured when conditions are met for IFB3. 

For more information, see 4.5.3, “HCA3- O (12x IFB) fanout (FC 0171)” on page 156. 

The maximum number of combined external coupling links (active CE LR, ICA SR links, and IFB LR) is 144 per IBM z14™ server. IBM z14™ servers support up to 256 coupling CHPIDs per CPC. A z14 coupling link support summary for z14 is shown in Figure 4-6. 

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When defining IFB coupling links (CHPID type CIB), HCD defaults to seven subchannels. A total of 32 subchannels are supported on only HCA2-O LR (1xIFB) and HCA3-O LR (1xIFB) on zEC12 and later when both sides of the connection use IFB protocol. 

Sysplex Coupling and Timing Connectivity:  IBM z14 M0x (M/T 3906) supports N-2 sysplex connectivity (z14M0x, z14 ZR1, z13, z13s, zEC12, and zBC12), while IBM z14 ZR1 supports only N-1 sysplex connectivity  (z14 M0x, z14 ZR1, z134, and z13s). 

In a Parallel Sysplex configuration, z/OS and CF images can run on the same or on separate servers. There must be at least one CF that is connected to all z/OS images, even though other CFs can be connected only to selected z/OS images. 

