Patent ID: 9052837
Filing Date: 2015-06-09
Classification: G06F

Abstract:
1. A computer program product for processing communications between a control unit and a channel subsystem in an input/output (I/O) processing system, comprising a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: sending a message in a command mode from the control unit to the channel subsystem of a host computer system, the control unit configured to control an I/O device and receive information from the host computer system and the control unit via a channel path, the command mode using a first protocol that supports Channel Command Word (CCW) channel programs configured to support at least one CCW that specifies a command for performing an I/O operation; receiving, by the control unit, a command in a transport mode from the channel subsystem at the control unit, the transport mode using a second protocol that supports Transport Control Word (TCW) channel programs configured to support at least one transport command control block (TCCB), the TCCB configured to hold a plurality of commands for performing an I/O operation; determining, by the control unit, whether the command is responsive to the message; determining, by the control unit, that a ships passing condition has occurred between the channel subsystem and the control unit based on the command being not responsive to the message and the command being sent on the same logical path as the message; and based on determining that the ships passing condition has occurred, determining by the control unit whether to perform one of i) executing the command and ii) terminating the command.