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Processing a variable length device command word at a control unit in an I/O processing system

  • US 7,840,717 B2
  • Filed: 02/14/2008
  • Issued: 11/23/2010
  • Est. Priority Date: 02/14/2008
  • Status: Active Grant
First Claim
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1. 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.

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