Abstract: A method, apparatus, and computer program product for processing a chained-pair linked transport control channel program in an I/O processing system is provided. The method includes receiving a first command message at a control unit specifying that a device command word (DCW) list is encoded in a data message associated with the first command message as part of the chained-pair linked transport control channel program. The method further includes receiving a second command message chained-pair linked to the first command message, the second command message specifying data attributes associated with the DCW list. The method additionally includes extracting the DCW list from the data message in response to receiving the data message, and executing the DCW list.

Abstract: A computer program product, apparatus, and method for providing exception condition feedback at a control unit to a channel subsystem in an I/O processing system are provided. 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. The method includes receiving a command message at the control unit from the channel subsystem, and detecting an exception condition in response to unsuccessful execution of at least one command in the command message. The method further includes identifying a termination reason code associated with the exception condition, writing the termination reason code to a response message, and sending the response message to the channel subsystem.

Abstract: A computer program product, an apparatus, and a method for reducing reserved device access contention at a control unit in communication with a plurality of operating systems via one or more channels are provided. 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 receiving a command message at the control unit from a first operating system, including an I/O operation command for a device. A device busy indicator is received, indicating that a second operating system has reserved the device. The command message is queued on a device busy queue in response to the device busy indicator. The control unit monitors for a device end indicator. The device busy queue is serviced to perform the I/O operation command in response to the device end indicator.

Abstract: A computer program product, apparatus, and method for facilitating input/output processing of a processing environment are provided.

Abstract: A computer program product, apparatus, and method for processing a transport control channel program with chain linked branching in an I/O processing system are provided. The method includes receiving a command message at a control unit from an I/O subsystem to perform an I/O operation. The method further includes reading a chain linked flag in the command message indicating that a subsequent command message for the I/O operation follows the command message. The method also includes reading a serialization flag in the command message requesting that device status be returned to the I/O subsystem in order to select the subsequent command message. The method additionally includes executing one or more commands in the command message, and transmitting the device status to the I/O subsystem in response to executing the one or more commands in combination with the serialization flag.

Abstract: A computer program product, apparatus, and method are provided for determining a state of an input/output (I/O) operation in an I/O processing system. A request from a channel subsystem is received at a control unit for performing the I/O operation. After a predetermined amount of time passes without the I/O operation completing, an interrogation request is received from the channel subsystem at the control unit for determining the state of the I/O operation. A response is sent from the control unit to the channel subsystem indicating the state of the I/O operation in response to the interrogation request. The response also includes information regarding a state of an I/O device executing the I/O operation and information indicating a state of the control unit controlling the I/O device executing the I/O operation.

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.

Abstract: Systems, methods and computer program products for providing indirect data addressing at an I/O subsystem of an I/O processing system. 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. The method includes receiving a control word for an I/O operation. The control word includes an indirect data address for data associated with the I/O operation. The indirect data address includes a starting location of a list of storage addresses that collectively specify the data, the list spans two or more non-contiguous storage locations. Data is gathered responsive to the list. The gathered data is transmitted to a control unit in the I/O processing system.

Abstract: A computer program product, an apparatus, and a method for processing communications between a target and an initiator an input/output processing system are provided. 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. The method includes: sending a message between the initiator and the target, the message requesting suspension of input/output operations between the initiator and the target for a period of time, the period of time being defined by the message; and responsive to the message, suspending input/output operation messages for the period of time.

Abstract: A computer program product, apparatus and method 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 includes a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method. The method includes receiving a DCW at the control unit from the I/O subsystem. The DCW specifies one or more I/O operations and includes a command, a control data count, and control data having a varying length specified by the control data count. The control data is extracted in response to the control data count. The command is then executed in response to the extracted control data to perform the specified one or more I/O operations.

Abstract: Input/output processing is facilitated by reducing communications between input/output communications adapters and control units during input/output processing. The number of exchanges and sequences between an input/output communications adapter and control unit is reduced by sending a plurality of commands from the adapter to the control unit as a single entity for execution by the control unit. The control unit executes the commands and provides the data, if any, in one sequence. The control unit relieves the adapter of the responsibility of tracking state of the individual commands and is able to calculate precise measurement data relating to execution of the commands.

Abstract: A computer program product, an apparatus, and a method for processing communications between a control unit and a channel subsystem in an input/output processing system are provided. 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.

Abstract: A bi-directional and full duplex facility for permitting both the IO processor and the Channel to write CCA messages on their respective queues at the same time. IOP messages to the channel are stored on the TO_CHN queue and Channel messages to the IOP on the TO_IOP queue. CCA Queues replace hardware CCAs due to increasing transmission capabilities of current IO processors and Channel processors. Even though the mechanism is similar, the present invention provides some benefits in the use of signaling. The IOP does not have to signal the Channel each time it puts something on its outbound queue. Each queue contains multiple slots. This allows the IOP and Channel to write multiple messages on the targeted queue without encountering a CCA busy signal. The actual queues are now structured in hardware system memory.

Abstract: A computer Input/Output system having a fabric, a control unit (CU) and a host computer including a channel, the channel having a channel port connected by a first link to a channel neighbor port of the fabric, and the control unit having a CU port connected by a second link to a CU neighbor port on the fabric. Then an error is detected in the link or protocol between the channel and the control unit, error data are reported to the channel by the channel, the channel port, the channel neighbor port, the control unit, the CU port and the CU neighbor port and sent to the channel. The error data are provided to the host computer for analysis.

Abstract: A computer program product, apparatus, and method for processing a transport control channel program with chain linked branching in an I/O processing system are provided. The method includes receiving a command message at a control unit from an I/O subsystem to perform an I/O operation. The method further includes reading a chain linked flag in the command message indicating that a subsequent command message for the I/O operation follows the command message. The method also includes reading a serialization flag in the command message requesting that device status be returned to the I/O subsystem in order to select the subsequent command message. The method additionally includes executing one or more commands in the command message, and transmitting the device status to the I/O subsystem in response to executing the one or more commands in combination with the serialization flag.

Abstract: A method, apparatus, and computer program product for processing a chained-pair linked transport control channel program in an I/O processing system is provided. The method includes receiving a first command message at a control unit specifying that a device command word (DCW) list is encoded in a data message associated with the first command message as part of the chained-pair linked transport control channel program. The method further includes receiving a second command message chained-pair linked to the first command message, the second command message specifying data attributes associated with the DCW list. The method additionally includes extracting the DCW list from the data message in response to receiving the data message, and executing the DCW list.

Abstract: A method, apparatus, and computer program product for processing a chain linked transport control channel program in an I/O processing system is provided. The method includes receiving a first command message at a control unit specifying a first predetermined sequence number for performing a first set of one or more commands as part of an I/O operation. The method further includes receiving a second command message specifying a second predetermined sequence number for performing a second set of one or more commands as part of the I/O operation. The method also includes comparing the sequence numbers to a next expected predetermined sequence number to determine an order of performing the commands. The method additionally includes executing the commands in the determined order to perform the I/O operation.

Abstract: A method and system are disclosed for generating a data logout in a computing environment having a processor and an input/output subsystem for receiving data from and sending data to the processor. The method comprises the steps of the input/output subsystem maintaining a defined set of data; at defined time, the processor issuing a data logout command; and sending said data logout command to the input/output subsystem. In response to receiving said data logout command, the input/output subsystem sends said defined set of data to a specified location. In a preferred implementation, the input/output subsystem includes a channel subsystem and a plurality of input/output devices, and the data logout command is sent to one of the input/output devices. Also, in the preferred embodiment, the channel subsystem includes a channel control unit function and the data logout command is sent to the channel control unit function.

Abstract: A computer Input/Output system having a fabric, a control unit (CU) and a host computes including a channel, the channel having a channel port connected by a first link to a channel neighbor port of the fabric, and the control unit having a CU port connected by a second link to a CU neighbor port on the fabric. When an error is detected in the link or protocol between the channel and the control unit, after a retry of the failing operation is performed, error data are reported to the channel by the channel, the channel port, the channel neighbor port, the control unit, the CU port and the CU neighbor port and sent to the channel. The error data are provided to the host computer for analysis.

Abstract: A method and system are disclosed for generating a data logout in a computing environment having a processor and an input/output subsystem for receiving data from and sending data to the processor. The method comprises the steps of the input/output subsystem maintaining a defined set of data; at defined time, the processor issuing a data logout command; and sending said data logout command to the input/output subsystem. In response to receiving said data logout command, the input/output subsystem sends said defined set of data to a specified location. In a preferred implementation, the input/output subsystem includes a channel subsystem and a plurality of input/output devices, and the data logout command is sent to one of the input/output devices. Also, in the preferred embodiment, the channel subsystem includes a channel control unit function and the data logout command is sent to the channel control unit function.