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Bi-directional data transfer within a single I/O operation

  • US 9,298,379 B2
  • Filed: 11/17/2014
  • Issued: 03/29/2016
  • Est. Priority Date: 02/14/2008
  • Status: Active Grant
First Claim
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1. A computer program product for facilitating input/output (I/O) processing for an I/O operation at a control unit coupled to an I/O device, the control unit configured for communication with a host computer system including a memory associated with an operating system, the host computer system including a channel subsystem, the computer program product comprising:

  • a non-transitory tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising;

    receiving, by the control unit, a command block transmitted from the channel subsystem as a single entity configured to hold a plurality of commands, the plurality of commands including at least one of an input command and an output command, the plurality of commands specified by a transport command word (TCW) obtained by the channel subsystem and associated with the I/O operation, the TCW specifying at least one of a location in the memory of output data and a location in the memory for storing input data, the TCW including a read indicator configured to indicate whether the I/O operation includes input data and a write indictor configured to indicate whether the I/O operation includes output data;

    based on the command block holding at least one output command, receiving the output data specified by the TCW and executing the at least one output command; and

    based on the command block holding at least one input command, forwarding the input data specified by the TCW to the channel subsystem for storage at a location specified by the TCW.

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