Abstract: I/O measurement data for channels attached to logical control unit queues is obtained related to a plurality of logical control unit queues. A store secondary queue measurement data instruction specifies a range of queues for which extended secondary measurement blocks derived from the I/O measurement data are stored at a memory address specified by the store secondary queue measurement data instruction.

Abstract: An Extended Input/output (I/O) measurement word facility is provided. Provision is made for emulation of the Extended I/O measurement word facility. The facility provides for storing measurement data associated with a single I/O operation in an extended measurement word associated with an I/O response block. In a further aspect, the stored data may have a resolution of approximately one-half microsecond.

Abstract: An Extended Input/output (I/O) measurement block facility is emulated. The facility provides for the collection of relevant I/O measurement data, and the storing for later efficient retrieval of that data in an extended measurement block. The stored data relates to the performance of an I/O subchannel.

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 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: Provided are a method, system, and article of manufacture for providing an address format compatible with different addressing formats used for addressing different sized address spaces. An address format is used in an operating system to address storage space in a storage device comprising a first region and a second region of storage space. A first group of applications uses the address format to only address the storage space in the first region and is not coded to use the address format to access the second region and a second group of applications uses the address format to address the storage space in the first and second regions.

Abstract: An apparatus, system, and method are disclosed for switching a volume address association in a point-in-time copy relationship. A copy module creates a point-in-time copy structure of a source volume at a target volume. A migration module copies data from the source volume to the target volume. A detection module detects data corruption in the source volume. A switch module switches a logical volume address from a source volume address of the source volume to a target volume address of the target volume in response to detecting the data corruption, redirecting data reads and writes to the target volume. In one embodiment, a tracking module tracks a current target volume copy of source volume data and redirects an access for source volume data without the current target volume copy to the source volume.

Abstract: Provided are a method, system, and article of manufacture for assigning alias addresses to base addresses. An assignment is provided of base addresses to the devices, wherein the base addresses are used to access the devices assigned to the base addresses. An assignment is provided of a plurality of alias addresses to an alias address pool. The alias addresses in the alias address pool are capable of being dynamically assigned to the devices to service I/O requests to the devices. An Input/Output (I/O) request to access one target device comprising one of the devices is processed. A determination is made as to whether the base address assigned to the target device is available. One alias address is assigned to the target device in response to determining that the base address is not available. The I/O request is issued to the assigned alias address to transmit the request to the target device.

Abstract: I/O measurement data associated with the performance of an I/O operation process is gathered during the I/O process. The I/O measurement data is saved in an IRB memory location specified by a test subchannel instruction. An I/O interrupt signals the completion of the I/O operation process.

Abstract: An apparatus, system, and method are disclosed for accessing a preferred path through a storage controller. A request module receives a request from a host to identify a preferred path from the host to a control unit image. A response module reports the preferred path to the host. A connection module connects the host through the preferred path to the control unit image. In one embodiment, a detection module detects a failure of a first interconnection module comprising the preferred path. The connection module may re-connect the host to the control unit image through a non-preferred path comprising a second interconnection module in response to the failure of the first interconnection module.

Abstract: A communication-path management system includes a path-detection component for identifying all communications paths between a host computer, through a controller, to a data storage device. Once identified, the communication paths are incorporated into a logical-path mask. The path-detection component recognizes each path as either preferred or non-preferred based on latency, bandwidth, availability, or other user-defined criteria and divides the logical-path mask into a preferred path subset and a non-preferred path subset. If a valid path exists in the preferred path subset, all communications from the host computer to the data storage device transit paths belonging to this subset. Otherwise, active control is given to the non-preferred path subset. A channel subsystem manages actual communication based on resource allocation and contention using the currently active subset.

Abstract: Provided are a method, system, and program for reassigning storage volumes from a failed processing system to a surviving processing system. A first processing system detects a failure of a second processing system. The first processing system determines device groups of storage devices managed by the failed second processing system and determines for each determined device group, hosts that connect to storage devices in the device group. The first processing system sends, for each device group, a unit check to each determined host indicating failure of each device group through one storage device in the device group to which the determined host connects. The determined hosts execute instructions to terminate any I/O operations in progress on the storage devices in the device group in response to the unit check indicating failure of one storage device in the device group and issue, a command to one storage device for the device group to end the busy condition.

Abstract: An Input/output (I/O) measurement block facility is provided that creates subchannel measurement blocks (comprising device busy values) related to performance of an I/O operation of a subchannel, wherein a device busy time value is a sum of time intervals when the subchannel is device busy during an attempt to initiate any one of a start function or a resume function at the subchannel.

Abstract: I/O measurement data for channels attached to logical control unit queues is obtained related to a plurality of logical control unit queues. A store secondary queue measurement data instruction specifies a range of queues for which extended secondary measurement blocks derived from the I/O measurement data are stored at a memory address specified by the store secondary queue measurement data instruction.

Abstract: I/O measurement data associated with the performance of an I/O operation process is gathered during the I/O process. The I/O measurement data is saved in an IRB memory location specified by a test subchannel instruction. An I/O interrupt signals the completion of the I/O operation process.

Abstract: Input/output (I/O) communications subadapters, such as subchannels, of an I/O subsystem are dedicated to components, such as I/O devices, of the I/O subsystem. The subadapters provide information about the associated components, in response to the execution of I/O instructions. To enhance I/O connectivity, a plurality of sets of I/O subadapters is provided to an operating system image. This allows programs of the operating system image to access a same component via different sets of I/O communications subadapters. Further, it enables an operating system image to use more than 64k subchannels.

Abstract: Disclosed is a system, method, and program for selecting one of multiple proposed paths to a device. For each proposed path, a determination is made of a number of components the proposed path shares with existing paths to the device. The components comprise points of failure such that if one component fails then the path including the component fails. The determined number of shared components for each proposed path is used to select one proposed path.