To enable the communication between a Coupling Facility (CF) Logical Partition and the z/OS LPARs, special types of high-speed CF links are required. These links are important because of the impact of link performance on CF request response times. For configurations covering large distances, time spent on the link can be the largest part of CF response time.
A CF link adapter can be shared between LPs, meaning the same adapter can transfer data from/to different z/OS systems to one CF, thus reducing the number of links needed. This is called Multiple Image Facility (MIF), the same name used for FICON and ESON channels.
CF links in the System z servers work in a mode called peer mode. In this mode we have even more flexibility with connections. For example, a single link adapter can be connected (multiple image facility) to both z/OS and a CF.
CF – Coupling Facility
ESCON – Enterprise Systems Connection
FICON – Fibre Connection
LP – Logical Partition
LPAR – Logical Partition
MIF – Multiple Image Facility