OPEN EXCHANGE LIMITING IN AN I/O PROCESSING SYSTEM
First Claim
1. A computer program product for limiting a number of open exchanges at a channel subsystem of an input/output (I/O) processing system using data from 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 command message to the control unit;
receiving a transport response information unit message at the channel subsystem in response to sending the command message to the control unit;
extracting a maximum control unit exchange parameter from the transport response information unit message as populated by the control unit;
determining a limit value for a maximum number of open exchanges between the channel subsystem and the control unit at the channel subsystem as a function of the extracted maximum control unit exchange parameter; and
applying the limit value to prevent opening of a new exchange.
1 Assignment
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Accused Products
Abstract
A computer program product, an apparatus, and a method for limiting a number of open exchanges at a channel subsystem of an I/O processing system using data from a control unit. The computer program product includes a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method that includes sending a command message to the control unit, and receiving a transport response information unit message in response. The method further includes extracting a maximum control unit exchange parameter from the transport response information unit message, and determining a limit value for a maximum number of open exchanges between the channel subsystem and the control unit as a function of the extracted maximum control unit exchange parameter. The method additionally includes applying the limit value to prevent opening of a new exchange.
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Citations
25 Claims
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1. A computer program product for limiting a number of open exchanges at a channel subsystem of an input/output (I/O) processing system using data from 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 command message to the control unit; receiving a transport response information unit message at the channel subsystem in response to sending the command message to the control unit; extracting a maximum control unit exchange parameter from the transport response information unit message as populated by the control unit; determining a limit value for a maximum number of open exchanges between the channel subsystem and the control unit at the channel subsystem as a function of the extracted maximum control unit exchange parameter; and applying the limit value to prevent opening of a new exchange. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus for limiting a number of open exchanges at a channel subsystem of an input/output (I/O) processing system, the apparatus comprising:
a channel subsystem in communication with a control unit, the channel subsystem performing a method comprising; sending a command message to the control unit; receiving a transport response information unit message at the channel subsystem in response to sending the command message to the control unit; extracting a maximum control unit exchange parameter from the transport response information unit message as populated by the control unit; determining a limit value for a maximum number of open exchanges between the channel subsystem and the control unit at the channel subsystem as a function of the extracted maximum control unit exchange parameter; and applying the limit value to prevent opening of a new exchange. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method for limiting a number of open exchanges at a channel subsystem of an input/output (I/O) processing system using data from a control unit, the method comprising:
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sending a command message to the control unit; receiving a transport response information unit message at the channel subsystem in response to sending the command message to the control unit; extracting a maximum control unit exchange parameter from the transport response information unit message as populated by the control unit; determining a limit value for a maximum number of open exchanges between the channel subsystem and the control unit at the channel subsystem as a function of the extracted maximum control unit exchange parameter; and applying the limit value to prevent opening of a new exchange. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. A computer program product for limiting a number of open exchanges at a channel subsystem of an input/output (I/O) processing system using data from 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 information unit message to the control unit including a transport command control block (TCCB) as part of a transport control word (TCW) channel program; setting a limit value equal to a default value until a transport response information unit message is received from the control unit, wherein the limit value establishes a maximum number of open exchanges between the channel subsystem and the control unit at the channel subsystem; receiving the transport response information unit message at the channel subsystem in response to sending the transport command information unit message to the control unit; extracting a maximum control unit exchange parameter from the transport response information unit message as populated by the control unit; determining the limit value as a function of the extracted maximum control unit exchange parameter, wherein the limit value is unmodified in response to the extracted maximum control unit exchange parameter with a value of zero; and applying the limit value to prevent opening of a new exchange to block a new I/O command from being output on the new exchange in response to a current number of open exchanges being greater than or equal to the limit value.
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25. An apparatus for limiting a number of open exchanges at a channel subsystem of an input/output (I/O) processing system, the apparatus comprising:
a channel subsystem in communication with a control unit, the channel subsystem performing a method comprising; sending a transport command information unit message to the control unit including a transport command control block (TCCB) as part of a transport control word (TCW) channel program; setting a limit value equal to a default value until a transport response information unit message is received from the control unit, wherein the limit value establishes a maximum number of open exchanges between the channel subsystem and the control unit at the channel subsystem; receiving the transport response information unit message at the channel subsystem in response to sending the transport command information unit message to the control unit; extracting a maximum control unit exchange parameter from the transport response information unit message as populated by the control unit; determining the limit value as a function of the extracted maximum control unit exchange parameter, wherein the limit value is unmodified in response to the extracted maximum control unit exchange parameter with a value of zero; and applying the limit value to prevent opening of a new exchange to block a new I/O command from being output on the new exchange in response to a current number of open exchanges being greater than or equal to the limit value.
Specification