Patent ID: 7840717

Claim:
A computer program product for processing a variable length device command word (DCW) at a control unit configured for communication with an input/output (I/O) subsystem in an I/O processing system, the computer program product comprising: a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: receiving a DCW at the control unit from the I/O subsystem via a transport command control block (TCCB) that includes a transport command area (TCA) header, a TCA where one or more DCWs are located, and a TCA trailer, the DCW specifying one or more I/O operations and including a command, a control data count, and control data having a varying length specified by the control data count; extracting the control data in response to the control data count; and executing the command in response to the extracted control data to perform the specified one or more I/O operations.