Abstract: A method of performing an input/output (I/O) processing operation includes: generating an address control structure for each of a plurality of consecutive data transfer requests, each address control structure specifying a local channel memory location of a corresponding address control word (ACW); receiving a data transfer request from a network interface that includes addressing information specified by a corresponding address control structure; comparing, by a data router in the channel, an Offset field of an address control structure and an Expected Offset field of an ACW to determine whether the data transfer request has been received in the correct order; and based on determining that the data transfer request has been received in the correct order, accessing the ACW by the data router and routing the data transfer request to a host memory location specified in the ACW.

Abstract: On embodiment includes a computer program product for performing a method including: obtaining information relating to an I/O operation at a channel subsystem in a host computer system; generating addressing information and forwarding the addressing information from at least one channel to a network interface between the channel subsystem and at least one I/O device, the addressing information specifying a location in a local channel memory; forwarding an I/O command message to the at least one I/O device via the network interface; responsive to the I/O command message, receiving a data transfer request from the network interface that includes the addressing information; responsive to receiving the data transfer request, accessing one of a plurality of address control words (ACWs), each ACW specifying an address of a location in a host computer memory; and routing the data transfer request to the host memory location specified in the ACW.

Abstract: Processing of out-of-order data transfers is facilitated in computing environments that enable data to be directly transferred between a host bus adapter (or other adapter) and a system without first staging the data in hardware disposed between the host bus adapter and the system. An address to be used in the data transfer is determined, in real-time, by efficiently locating an entry in an address data structure that includes the address to be used in the data transfer.

Abstract: A method of performing an input/output (I/O) processing operation includes: generating at least one address control word (ACW) specifying one or more host memory locations for transfer of data between a host computer system and a control unit, and storing the at least one ACW in the local channel memory; generating an address control structure for each data transfer specified by the I/O operation and forwarding each address control structure from the at least one channel to the network interface; forwarding an I/O command message to the at least one I/O device via a network interface; receiving a data transfer request from the network interface that includes the address control structure; and routing the data to at least one host memory location specified by the corresponding ACW or routing the data from a host memory location specified by the ACW to the network interface.

Abstract: A method of performing an input/output (I/O) processing operation includes obtaining information relating to an I/O operation at a channel subsystem in the host computer system, the channel subsystem including at least one channel having a channel processor and a local channel memory, generating addressing information and forwarding the addressing information to a network interface between the channel subsystem and at least one I/O device, the addressing information specifying a location in the local channel memory. The method also includes forwarding an I/O command message to the at least one I/O device via the network interface, receiving a data transfer request from the network interface that includes the addressing information, accessing one of a plurality of address control words (ACWs), each ACW specifying an address of a location in a host computer memory, and routing the data transfer request to the host memory location specified in the ACW.

Abstract: A computer program product for performing input/output (I/O) processing is configured for performing a method including: obtaining information relating to an I/O operation at a channel subsystem; generating and storing in local channel memory at least one address control word (ACW) specifying one or more host memory locations for data transfer and including a field for storing header information; generating an address control structure specifying a location in the local channel memory of a corresponding ACW; receiving a data transfer request from a network interface that includes the address control structure; responsive to an input data request, routing the data to at least one host memory location specified by the corresponding ACW and storing header information in the corresponding ACW; and responsive to an output data request, routing the data from a host memory location specified by the ACW to the network interface and appending header information to the data.

Abstract: A method of performing an input/output operation includes: generating by a channel subsystem at least one command message including one or more device command words (DCWs), at least one DCW including a data count and a suppress-length indication (SLI) configured to instruct a control unit whether to continue to perform the I/O operation in response to an incorrect length condition; forwarding the at least one command message to the control unit; receiving an incorrect length (IL) value from the control unit and storing an IL indicator in a subchannel-status word, the IL indicator representing the IL value, the IL value being a first IL value in response to a first SLI value and the data count not matching the amount of data required, the IL value being a second IL value in response to a second SLI value and the data count not matching the amount of data required.

Abstract: A method for detecting virtual images in a network, the network including a host system and a plurality of physical devices in operable communication with one another, includes forming a query packet at the host system; providing the query packet to at least one of the plurality of physical devices; forming at the at least of the plurality of physical devices a first vector in response to the query packet, the first vector including a bit for each possible virtual image that may be formed in the at least one of the plurality of devices and indicating which of the virtual images are configured and addressable; and providing the first vector to the host system.

Abstract: A computer system includes a processor configured for detecting initial command response times of a plurality of paths for transmitting signals from the processor to one or more external devices via a plurality of channels, assigning weighted values to the plurality of paths based on the detected initial command response times, and modifying a frequency at which respective paths among the plurality of paths are selected for transmitting the signals based on the weighted values assigned to the respective paths.

Abstract: 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: obtaining a transport command word (TCW) for an I/O operation, 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; 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 one or more I/O commands; gathering 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 forwarding the message to the control unit for execution.

Abstract: A computer program product for performing input/output (I/O) processing is provided. The computer program product is configured to perform: obtaining information relating to an I/O operation at a channel subsystem; generating and storing in local channel memory at least one address control word (ACW) specifying one or more host memory locations for data transfer and including a data check word generation field and/or a data check word save field; responsive to receiving an input data transfer request including at least one data check word, storing the at least one data check word in the data check word save field and performing a check of the data to determine whether the data has been corrupted; and responsive to receiving an output data transfer, generating at least one data check word based on the data check word generation field and appending the at least one data check word to the data.

Abstract: An input/output processing method includes generating and storing at least one address control word (ACW) including a data check word generation field and/or a data check word save field in local channel memory of a channel subsystem, and generating and forwarding to a network interface an address control structure specifying a location in the local channel memory of a corresponding ACW. The method also includes, responsive to a data transfer request, storing the at least one data check word in the data check word save field and routing the data to a host memory location specified by the corresponding ACW responsive to performing a check of the data and determining that the data has not been corrupted, or retrieving the data based on the corresponding ACW, generating and appending at least one data check word and routing the data and the at least one data check word to the interface.

Abstract: A computer program product, apparatus, and a 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 method includes receiving a command block from the channel subsystem, the command block including at least one input command and at least one output command specified by a transport command word (TCW) and associated with the I/O operation, the I/O operation having both input and output data, the TCW specifying a location in the memory of the output data and a location in the memory for storing the input data; receiving the output data specified by the TCW and executing the at least one output command; and forwarding the input data specified by the TCW to the channel subsystem for storage at a location specified by the TCW.

Abstract: Processing of out-of-order data transfers is facilitated in computing environments that enable data to be directly transferred between a host bus adapter (or other adapter) and a system without first staging the data in hardware disposed between the host bus adapter and the system. An address to be used in the data transfer is determined, in real-time, by efficiently locating an entry in an address data structure that includes the address to be used in the data transfer.

Abstract: A computer program product is provided for performing an input/output (I/O) processing operation at a host computer system. The computer program product is configured to perform: obtaining a transport command word (TCW) at a channel subsystem for an I/O operation, the TCW including an address of a transport command control block (TCCB) having a transport command area (TCA) configured to hold a first plurality of device command words (DCW) and control data associated with respective DCWs, the first plurality of DCWs including a transfer TCA extension (TTE) DCW that specifies a TCA extension, the TCA extension configured to hold one or more DCWs and control data associated with respective DCWs; gathering the TCCB from one or more locations specified in the TCCB address and transferring the TCCB to the control unit; gathering the TCA extension specified by the TTE DCW; and transferring the TCA extension to the control unit.

Abstract: A method of performing an input/output operation includes: generating by a channel subsystem at least one command message including one or more device command words (DCWs), at least one DCW including a data count and a suppress-length indication (SLI) configured to instruct a control unit whether to continue to perform the I/O operation in response to an incorrect length condition; forwarding the at least one command message to the control unit; receiving an incorrect length (IL) value from the control unit and storing an IL indicator in a subchannel-status word, the IL indicator representing the IL value, the IL value being a first IL value in response to a first SLI value and the data count not matching the amount of data required, the IL value being a second IL value in response to a second SLI value and the data count not matching the amount of data required.

Abstract: 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 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 the host computer system obtaining a transport command word (TCW) for an I/O operation. The TCW specifies a location of one or more I/O commands and a flag set to indicate that the location is an indirect address. The host computer system extracts the location of the one or more I/O commands and the flag from the TCW, gathers the one or more I/O commands responsive to the location specified by the TCW and the flag, and then forwards the one or more I/O commands to the control unit for execution.

Abstract: An article of manufacture, apparatus, and a 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 method includes the host computer system obtaining a transport command word (TCW) for an I/O operation having both input and output data. The TCW specifies a location of the output data and a location for storing the input data. The host computer system forwards the I/O operation to the control unit for execution. The host computer system gathers the output data responsive to the location of the output data specified by the TCW, and then forwards the output data to the control unit for use in the execution of the I/O operation. The host computer system receives the input data from the control unit and stores the input data at the location specified by the TCW.

Abstract: A method includes configuring a processing circuit to perform: receiving a control word for an I/O operation, forwarding a transport command control block (TCCB) from the channel subsystem to a control unit, gathering data associated with the I/O operation, and transmitting the gathered data to the control unit in the I/O processing system. Gathering the data includes accessing entries of a list of storage addresses that collectively specifying the data. Based on an entry of the list comprising a not-set first flag and a corresponding first storage address, gathering data from a corresponding storage location, and based on an entry of the list comprising a set first flag and a corresponding second storage address, obtaining a next entry of the list from a second storage location.

Abstract: A computer program product is configured for performing a method including: generating at least one command message by a channel subsystem of the host computer system, the at least one command message including one or more device command words (DCWs), wherein at least one DCW of the one or more DCWs includes a suppress-length indication (SLI) configured to instruct a control unit to continue to perform the I/O operation in response to the control unit detecting that the data count does not match an amount of data required; receiving an incorrect length (IL) value, the IL value being a first IL value in response to the SLI being a first SLI value and the data count not matching the amount of data required; and responsive to receiving the IL value from the control unit, storing an IL indicator in a subchannel-status word.