International Business Machines Corporation

William C Shepard

Harry M Yudenfriend

Allan Samuel Meritt

Dale Francis Riedy, Jr

Jeffrey Mark Nick

David Harold Surman

Michael D Swanson

James Elkins McIlvain

David Arlen Elko

Scott Brady Compton

Jeffrey Alan Frey

Robert Frederic Kern

Brian B Moore

Tabor R Powelson

Tri M Hoang

Larry Richard Perry

John F Betz

John F Isenberg, Jr

Michael Aloysius Paulsen

Lisa M Goetze

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.

Data consistent freeze of peer-to-peer remote copy in a multiple computing cluster environment

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.

Detection and recovery of lost host enabled facilities

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.

Data integrity mechanism for external storage devices

A logical positioning mechanism is provided within a storage controller, thus enabling the storage controller to determine which logical position in a storage device is to be accessed next. The logical positioning mechanism includes one or more logical position indicators defined, maintained and controlled by the storage controller. The logical position indicators include the address of the logical position to be next accessed and are incremented and decremented by the storage controller depending upon the operation accessing the logical position.

Logical positioning within a storage device by a storage controller

A disaster recovery system providing remote data shadowing between a primary and a secondary site uses a method and apparatus for swapping, or switching, host directed I/O operations from a primary data storage device to a secondary data storage device in a remote copy duplex pair. Application programs running in a host processor at the primary site first quiesce all I/O operations and record updates targeted to the primary data storage device. The remote copy duplex pair is checked to verify that the secondary data storage device is a fully synchronized copy of the primary data storage device. The secondary data storage device is then swapped with the primary data storage device by terminating the remote copy duplex pair, establishing an opposite direction remote copy duplex pair such that the secondary data storage device is a primary device of the duplex pair and the primary data storage device is a shadowing device, and updating the application programs running in the primary host processor with a device address of the secondary data storage device substituted as a device address of the primary data storage device. Finally, the primary host processor resumes its application programs such that subsequent I/O operations and record updates targeted for the primary data storage device are directed through a secondary storage controller to the secondary data storage device, and copied to the primary data storage device.

Concurrent switch to shadowed device for storage controller and device

Apparatus and accompanying methods for use in preferably a multi-system shared data (sysplex (5)) environment which quickly and efficiently isolates (fences), through a pre-defined hierarchical order, failed sysplex components from accessing shared data in order to protect data integrity. Specifically, by dividing a sysplex workload into specified fence groups (FG A, FG B) and providing appropriate software and hardware fence support, fencing can occur at various distinct levels: a member-to-member level, i.e. to allow any member (220, 225, 230, 233,237) of a fence group to fully isolate any other ('target') member of that same group; a fence group level, i.e. to isolate all members of a fence group that execute on a 'target' system (200.sub.1, 200.sub.2, 200.sub.3); and a system level, i.e. to fully isolate an entire 'target' system. Through pre-defined escalation rules (630), fencing can be escalated from a lower member level to a higher, group or system, level in the event a lower level fence can not be successfully imposed. Member level fencing is accomplished in software (1300, 1500); group and system level fencing is accomplished through dedicated hardware fencing facilities (44). An identifier (444, 464) uniquely designates each different fence group existing on a computer processing complex (CPC) (40.sub.1, 40.sub.2, 40.sub.3, 40.sub.M) in the sysplex over the life of that CPC. Advantageously, this technique eliminates erroneous back level fencing, significantly expedites fence processing and also greatly reduces a need for human intervention.

Apparatus and accompanying method for use in a sysplex environment for

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.

Interdicting I/O and messaging operations from sending central

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.

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Hyde Park, NY, United States of America

William C Shepard