Abstract: A method according to one approach is for avoiding use of paths of a communication multipath attached to an input/output (I/O) control unit. The method includes: receiving, from a host, a define subsystem operation (DSO) define path usage command configured to instruct the I/O control unit of expected usage of one or more specified paths. The DSO define path usage command includes: a set first flag, the first flag being configured to restrict or allow multipath reconnections for the specified path(s) and the particular path group. The DSO define path usage command also includes a set second flag, the second flag being configured to restrict or allow the specified path(s) and the particular path group to present unsolicited status. The DSO define path usage command includes a filled list of interface identifications determining the respective specified path(s), and a path group identification determining the particular path group.

Abstract: Data consistent freeze of peer-to-peer remote copy in a multiple computing cluster environment includes freezing, by each of a first computing cluster and a second computing cluster, non-shared logical volumes of the first computing cluster and the second computing cluster; freezing, by each of the first computing cluster and the second computing cluster, shared logical volumes of the first computing cluster and the second computing cluster, wherein a key logical volume is a last shared logical volume to be frozen; selecting one of the first computing cluster and the second computing cluster to perform thaws of the shared logical volumes based on which of the first computing cluster or the second computing cluster was the last to freeze the key logical volume; and thawing, by the selected one of the first computing cluster and the second computing cluster, the shared logical volumes.

Abstract: Data consistent freeze of peer-to-peer remote copy in a multiple computing cluster environment includes freezing, by each of a first computing cluster and a second computing cluster, non-shared logical volumes of the first computing cluster and the second computing cluster; freezing, by each of the first computing cluster and the second computing cluster, shared logical volumes of the first computing cluster and the second computing cluster, wherein a key logical volume is a last shared logical volume to be frozen; selecting one of the first computing cluster and the second computing cluster to perform thaws of the shared logical volumes based on which of the first computing cluster or the second computing cluster was the last to freeze the key logical volume; and thawing, by the selected one of the first computing cluster and the second computing cluster, the shared logical volumes.

Abstract: Coordinating an unplanned swap event across multiple computing clusters includes receiving a notification from each of a plurality of computing clusters through a shared storage device of a set of storage devices. The notification identifies which of a first set of target storage devices and a second set of target storage devices that a particular computing cluster of the plurality of computing clusters is capable of swapping to from a set of source storage devices. Based on the notification from each of the plurality of computing clusters, it is determined whether the plurality of computing clusters will swap from usage of the set of source storage devices to the first set of target storage devices or to the second set of target storage devices during a swap event.

Abstract: A method, system, and computer program product are provided for determining whether a control unit for an attached device has lost knowledge of a supported host enabled facility associated with the attached device. I/O instructions are initiated that include a first instruction to determine whether the control unit currently has knowledge of the host enabled facility and a second instruction providing knowledge of the host enabled facility by the control unit. Based on responses from the control unit to the I/O instructions, it is determined whether the control unit has transitioned from not having knowledge of the host enabled facility to having such access. If it is determined that the control unit has made such transition as a result of the sequence of I/O instructions, parameters for use with the host enabled facility are initialized; otherwise, such initialization is prevented.

Abstract: A method, system, and computer program product are provided for determining whether a control unit for an attached device has lost knowledge of a supported host enabled facility associated with the attached device. I/O instructions are initiated that include a first instruction to determine whether the control unit currently has knowledge of the host enabled facility and a second instruction providing knowledge of the host enabled facility by the control unit. Based on responses from the control unit to the I/O instructions, it is determined whether the control unit has transitioned from not having knowledge of the host enabled facility to having such access. If it is determined that the control unit has made such transition as a result of the sequence of I/O instructions, parameters for use with the host enabled facility are initialized; otherwise, such initialization is prevented.

Abstract: A method for maintaining data integrity of a storage device is provided. A request is received to create an access monitoring session for a data range on a volume of the storage device. A session identification (ID) is determined for the access monitoring session for data range on the volume. An entry is created in an access monitoring session table for the session ID, and the entry adds the access monitoring session with session ID for the data range on the volume to the access monitoring session table. Request parameters are included in the request to create the access monitoring session. The request parameters denote access to the data range on the volume for the session ID and are stored in the access monitoring session table. Access is controlled to the data range on the volume for the session ID based on request parameters stored in the access monitoring session table.

Abstract: A method for maintaining data integrity of a storage device is provided. A request is received to create an access monitoring session for a data range on a volume of the storage device. A session identification (ID) is determined for the access monitoring session for data range on the volume. An entry is created in an access monitoring session table for the session ID, and the entry adds the access monitoring session with session ID for the data range on the volume to the access monitoring session table. Request parameters are included in the request to create the access monitoring session. The request parameters denote access to the data range on the volume for the session ID and are stored in the access monitoring session table. Access is controlled to the data range on the volume for the session ID based on request parameters stored in the access monitoring session table.

Abstract: In a multi-system complex having central processing complexes (CPCs) and subsystems, a hardware facility for prompt interdicting I/O and message operations. A CPC or subsystem failure causes as interruption in the availability of the data bases to the attached network of terminals. Often such networks have thousands of terminals. Even a short loss of data is detrimental. Therefore the CPC or subsystem takeover must be accomplished as quickly as possible and the I/O attached to the failing CPC or subsystem must be interdicting to release it for use to the rest of the complex. The disclosed hardware facility provides a mechanism which is program initiated and controlled and which guarantees the prompt completion of the interdiction function.

Abstract: An I/O request time limit value is set in a request-based, device-based, data-set-based, or workload-based time limit field, for transactions performing I/O operations to I/O devices in a data processing system. A scan routine compares the total time for the I/O request (including waiting time and retry time) against the appropriate time limit(s), and terminates the I/O request if the time limit is exceeded. If an active I/O request is interrupted as a result of an I/O error, retry is prohibited if the total I/O request time (including retry time) exceeds the appropriate time limit, or is within a threshold value of the appropriate time limit.