Brocade FICON Administrator’s Guide (Supporting Fabric OS v7.3.0) - Manual (Page 87)

Emulation topology
FICON device emulation topologies have unique requirements due to the characteristics of the
emulation devices. Each device must track the emulated sessions and maintain the state of the
emulated devices in order to satisfy both ends of the connection. Because this is done over very long
distances, care must be taken when configuring the ISL connections to insure that the sessions remain
along exclusive paths. By maintaining an exclusive path between the emulation units, the recovery
scenarios become manageable and allow system-level mechanisms to take precedence, such as
device level recovery at the channel or control unit.
Generally, channel-to-control unit access is deployed as a one-to-many topology where one channel is
defined to access many control units. FICON environments, however, are deployed in multiple
redundant configurations that also define access from one control unit to many channels. When
emulation is involved, these configurations can result in overlapping channel and control unit
Emulation topology
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