International Business Machines Corporation

James Lincoln Iskiyan

Brent Cameron Beardsley

Roger Gregory Hathorn

William Frank Micka

Bret Wayne Holley

Harry M Yudenfriend

Michael T Benhase

Robert Frederic Kern

Vernon John Legvold

Joseph C Elliott

Robert Wesley Shomler

Michael Aloysius Paulsen

James Elkins McIlvain

Peter L Leung

Cortland D Starrett

John R Wolfe

Asim R Qureshi

Guy E Martin

William G Thompson

Philip Ray Mills

Disclosed is a system, method, and program for managing I/O operations transmitted from a computer system to a processing unit. The processing unit manages access to a storage device and executes the I/O operation against the storage device. The processing unit receives indication that a request to connect between the processing unit and the computer system failed. Upon receiving a subsequent I/O operation from the computer system after receiving indication that the connect request failed, the processing unit returns busy to the computer system initiating the subsequent I/O operation in response to receiving indication that the connect request failed. The connect request is retried after returning busy.

System, method, and program for handling failed connections in an input/output (I/O) system

A peer-to-peer backup storage system automatically switches from a primary storage site to a mirrored backup site in response to a primary site failure, where the secondary site then honors any existing host initiated reservation of primary storage. Each site includes a storage controller and storage, where the primary site receives and stores data and forwards the received data to the secondary site for storage to mirror contents of primary storage. The primary and secondary sites are coupled to one or more hosts. Whenever the primary controller receives a reserve request from a host, it reserves the primary storage (or a subpart thereof) for the exclusive use of the reserve-initiating host. This may involve, for example, the primary controller storing a path group ID that identifies the reserving host. The primary controller also notifies the secondary controller of the reservation, e.g., sending the path group ID involved in the reservation operation to the secondary site. Responsive to a primary site failure, the system performs &ldquo;switch&rdquo; operation where the system stops forwarding data from the primary site to the secondary site. Furthermore, the secondary site is operated in substitution for the primary site, to receive and store data from the hosts. Importantly, the secondary site honors the existing reservation of the primary storage by reserving the secondary storage to the first reserve-initiating host.

Peer-to-peer backup system with failure-triggered device switching honoring reservation of primary device

Disclosed is a system and method for processing a data access request (DAR). A processing unit, such as a storage controller, receives a DAR, indicating data to return on a channel, such as a channel connecting to a host system, and priority information for the received DAR. The processing unit retrieves the requested data for the received DAR from a memory area, such as a cache or direct access storage device (DASD), and determines whether there is a queue of data entries indicating retrieved data for DARs to transfer on the channel. The queued DARs include priority information. The processing unit processes at least one data entry in the queue, the priority information for the data entry, and the priority information for the received DAR to determine a position in the queue for the received DAR. The processing unit then indicates that the received DAR is at the determined position in the queue and processes the queue to select retrieved data to transfer on the channel to the host system.

Input/output data access request with assigned priority handling

Disclosed is a system for handling an input/output (I/O) operation. A controller, such as a storage controller, receives an I/O operation against an address for an I/O device, such as a volume in a storage system. The controller determines whether there is at least one active I/O operation executing against the I/O device. After determining that there is at least one active I/O operation, the controller determines whether the received I/O operation conflicts with active I/O operations executing against the I/O device. The controller then executes the received I/O operation against the I/O device concurrently with the active I/O operations after determining that the received I/O operation does not conflict with active I/O operations.

Input/output operation request handling in a multi-host system

Disclosed is a system for performing input/output (I/O) operations with a processing unit. A processing unit, such as a host system, determines a base and associated alias addresses to address an I/O device, such as a direct access storage device (DASD). The processing unit associates the determined base and alias addresses to the I/O device. The association of base and alias addresses is maintained constant for subsequent I/O operations until the processing unit detects a reassignment of the association of base and alias addresses. The processing unit then determines an available base or alias address to use with an I/O operation and may concurrently execute multiple I/O operations against the I/O device using the base and alias addresses.

System for accessing an input/output device using multiple addresses

A method for establishing bilateral communications over a single ESCON link coupling a pair of control units. The method steps include (a) permitting link address acquisition between directly connected link-level facilities that simultaneously assume the role of a master control unit in a peer-to-peer remote copy (PPRC) configuration, (b) resolving conflicting device-level frames that initiate a path to a device (also termed an I/O connection), and (c) dynamically determining the role assumed by a link-level facility (master or slave) when a single logical path is shared.

Method and means for bidirectional peer-coupled communication across a

A data storage system atomically suspends multiple duplex pairs across either a single storage subsystem or multiple storage subsystems. The duplex pairs are suspended such that the data on the secondary DASDs of the duplex pairs is maintained in a sequence consistent order. A host processor in the data storage system running an application generates records and record updates to be written to the primary DASDs of the duplex pairs. The storage controller directs copies of the records and record updates to the secondary DASDs of the duplex pairs. Sequence consistency is maintained on the secondary DASDs by quiescing the duplex pairs and then suspending the duplex pairs with change recording. Quiescing the duplex pairs allows any current write I/O in progress to complete to the primary DASD. The storage controller then locks out any subsequent write I/O from the host processor by raising a long busy signal to such subsequent write requests. Suspending the duplex pairs with change recording directs the storage controller to mark the physical address of the primary DASD which the application in the host processor updates between the time the duplex pair is suspended and then is reestablished.

Method and apparatus for suspending multiple duplex pairs during back up

A remote copy system incorporates dynamically modifiable ports on the storage controllers such that those ports can operate either as a control unit link-level facility or as a channel link-level facility. When configured as a channel link-level facility, a primary storage controller can appear as a host processor to a secondary storage controller. The primary storage controller can thereafter initiate multiple request connects (RQC) concurrently for servicing a single I/O request. In this manner, a first available path can be selected and system throughput thus improved since RQCs so not need to be sent serially from path to path looking for an available path.

Remote copy system for setting request interconnect bit in each adapter

A remote copy system incorporates dynamically modifiable ports on the storage controllers such that those ports can operate either as a control unit link-level facility or as a channel link-level facility. When configured as a channel link-level facility, a primary storage controller can appear as a host processor to a secondary storage controller. Using dynamic switches coupled between primary and secondary sites, fewer ESCON communication links are required since the ESCON communication links can function either as a channel or as storage controller communication link.

Remote data shadowing using a multimode interface to dynamically

A data processing system regulating access from a plurality of host computers to a plurality of direct access storage devices. The data processing system has a storage controller connected for data communication to the host computers by one or more channels per host computer. The storage controller is further connected to direct access storage devices used to provide auxiliary storage. The storage controller, responsive to host computer request, selectively establishes a communication link for data transfer between the host computers and the direct access storage devices. Channels are temporarily disqualified from obtaining control of the storage controller or a storage device during periods of contention for access to the storage devices or the storage controller. Transmission of device end and control unit end signals is also selective by channel. Override conditions are specified to allow for host computer or channel failure without disabling the data processing system.

System and method for regulating access to direct access storage devices

Data is accessed by record identification in a peripheral sub-system having cache and back store to transfer the most recently updated version of one or more records stored in the subsystem where one version of a record may be in a back store and a modified version of the record may be in a cache storage, by a method and apparatus including table lookup means for indicating for each record of each track of each device in said back store whether record data stored in cache is modified with respect to a version of the same record stored in back store; and means responsive to the indicating means for transferring the modified or backing store version of a record in accordance with predetermined criteria.

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Tucson, AZ, United States of America

James Lincoln Iskiyan