Channel extenders work in an XRC configuration when the system data mover is at either the primary site or the remote site. An XRC configuration with a channel extender operates most efficiently when the SDM software runs on a system at the secondary location. The system data mover then accesses the primary disks through the channel extender connection.
There may be situations where you cannot or do not want to have a continuously running host at the secondary site. If so, you can run the SDM on a system at the primary location with the channel extender that is connected to disk at the secondary location. This setup, however, is much less efficient than the previously mentioned configuration.
High quality channel extenders are transparent to the I/O software (except for the performance cost). XRC software can access primary or secondary disks that are configured through extenders.
For additional information about DASD channel extenders, refer to Using channel extenders.