PROVIDING INDIRECT DATA ADDRESSING FOR A CONTROL BLOCK AT A CHANNEL SUBSYSTEM OF AN I/O PROCESSING SYSTEM

摘要

An computer program product, apparatus, and method for facilitating input/output (I/O) processing for an I/O operation at a host computer system configured for communication with a control unit. The computer program product is provided for performing a method including: sending a transport command word (TCW) to an I/O subsystem, the TCW specifying a location address and indicating whether the TCW directly or indirectly addresses a message; extracting the location address from the TCW; obtaining the message from the specified location address based on the TCW indicating direct addressing, the message including the one or more I/O commands; gathering the one or more I/O commands from command locations specified by a list of addresses identified by the specified location address to form the message based on the TCW indicating indirect addressing; and generating a message including the one or more I/O commands.

主权项

1. A computer program product for facilitating input/output (I/O) processing for an I/O operation at a host computer system configured for communication with a control unit, 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: sending a transport command word (TCW) for an I/O operation from a host computer to an I/O subsystem, the TCW specifying a location address and indicating whether the TCW directly or indirectly addresses a message for transmitting one or more commands to the control unit; receiving the TCW at the I/O subsystem; extracting the specified location address from the TCW; obtaining the message from the specified location address based on the TCW indicating direct addressing, the message including the one or more I/O commands; gathering the one or more I/O commands from command locations specified by a list of addresses identified by the specified location address to form the message based on the TCW indicating indirect addressing; and generating a message including the one or more I/O commands.