This attention message indicates that a SETCACHE command to establish or re-establish a duplex pair was issued, and the requested devices were not on separate storage facilities. This attention is also issued when the devices are on separate 2-path strings having the same string address in a DLSE mode subsystem with intermixed 2-path and 4-path DASD strings. Separate storage facilities are recommended to avoid single points of failure when duplexing. The SETCACHE commands that could cause this attention message to be generated are:

• SETSECONDARY, if the prospective primary and secondary devices are on the same storage facility.
• REESTABLISHDUPLEX, if the primary device and the requested alternate device are on the same storage facility.