Using channel extenders

Remote copy supports channel extenders for instances where a direct ESCON® or Fiber connection is not possible, or where the performance overhead is too severe. Channel extenders perform the following functions:

Allow you to configure remote copy between locations that are either beyond the maximum ESCON channel distance, or where ESCON fiber optic cables cannot physically be placed.
Operate as a pair of devices. One device attaches to a host system channel and the second unit connects to the storage control, which considers the attached extender to be a system channel. Both devices are connected through a network of fiber-optic cables or telecommunication lines.

An advantage of XRC is that it minimizes the effect on applications when data moves across long distances. Channel extenders provide an important part of this solution. There may be a small delay between the time that the application makes the update and when the system data mover receives the update. This potential delay is a result of the time that is required for signals to travel greater distances and the channel-to-network protocol translation necessary to achieve transmission at the extended distance.

For PPRC extended distance operations, channel extenders are used when the primary and secondary storage control sites are separated by very long distances. For information, see Managing PPRC extended distance mode.