Patent ID: 8549185
Filing Date: 2013-10-01
Classification: G06F

Abstract:
1. A computer program product for performing an input/output (I/O) operation initiated by an I/O operation instruction at a host computer system configured for communication with a control unit, the computer program product comprising: a non-transitory machine-readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: obtaining a transport command word (TCW) at a channel subsystem in the host computer system for an I/O operation, the TCW including a transport command control block (TCCB) address field for locating at least one address of a TCCB, the TCCB including a transport command area (TCA) configured to hold a first plurality of device command words (DCWs) and control data associated with respective DCWs, the first plurality of DCWs including a transfer TCA extension (TTE) DCW that specifies a TCA extension, the TCA extension configured to hold one or more DCWs and control data associated with respective DCWs; gathering the TCCB from one or more locations specified in the TCCB address field and transferring the TCCB to the control unit; gathering the TCA extension specified by the TTE DCW; and transferring the TCA extension to the control unit.