Processing of data to determine compatability in an input/output processing system

摘要

A computer program product, an apparatus, and a method for processing communications between a control unit and a channel subsystem in an input/output processing system are provided. The computer program product includes a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method including: sending a message from the channel subsystem to the control unit in a first mode; receiving a response from the control unit and determining from the response whether the control unit supports a message protocol; and responsive to the message protocol being supported by the control unit, sending another message using the message protocol from the channel subsystem to the control unit to determine whether the control unit supports a second mode.