International Business Machines Corporation

William G Sherman, Ii

Vernon John Legvold

Chan Y Ng

Julia Liu

Michael T Benhase

Brent Cameron Beardsley

Susan Kay Candelaria

Joseph S Hyde, Ii

Adalberto Guillermo Yanes

Michael Howard Hartung

James C Chen

Mark Albert Reid

Dean Lee Hanson

Donald M Nordahl

Joel H Cord

Jeffrey R Steffan

Carol Santich Michod

Steven Richard Van Gundy

Kenneth Wayne Lane

Robert L Kwok

A method and means within a hierarchical, demand/response DASD subsystem of the passive fault management type in which, upon the occurrence of fault, error, or erasure, a long device busy signal of finite duration is provided to a host CPU. Any DASD storage device subject to the anomaly is isolated from any host inquiry during this interval. These measures permit retry or other recovery procedures to be implemented transparent to the host and the executing application. This avoids premature declarations of faults, errors, or erasures and consequent host application aborts and other catastrophic measures. If the detected anomaly is not resolved within the allotted time, then other data recovery procedures can be invoked including device reset, the status reported to the host, and the next request processed.

Method and means for utilizing device long busy response for resolving

A system and method for changing the number of logical volumes in a drawer in a rack in a direct access storage device subsystem is disclosed. The method and system are able to change the number of logical volumes without disrupting access to the other logical volumes in the rack. Channel connection addresses, which are logical volume addresses as known by the CPUs, are freed by removing the old drawer and then are mused. If the new drawer has more logical volumes than the old drawer, the next unused channel connection addresses are used with the new drawer. In a subsystem having a storage controller for providing control for a plurality of direct access storage devices, the logical volumes are spread across multiple physical devices. The storage controller maintains configuration data for the entire subsystem in redundant, non-volatile storage locations reserved specifically for its use. Each logical volume address for the rack is set by the drawer location and the logical sequence of the volumes within the drawer. As drawers are installed, the control unit sequentially assigns the volume addresses for the control unit and the channel connection addresses for the CPUs.

Method and system for maintaining concurrent data access during device

An adaptive hierarchical cache management system for improving effective cache hit ratios by eliminating unnecessary duplicate cache entries in two coupled cache memories. When a cached Storage Controller (SC) is coupled to a Cached Storage Drawer (CSD), the hierarchical coupling of the SC cache memory and CSD cache memory unnecessarily duplicates cache entries during normal operation. A Conditional Purge procedure purges duplicate lines from the CSD cache subject to a DASD activity threshold. A Prenotify Intent parameter allows the SC to request restaging of the purged cache entry preparatory to fast write or LRU demotion in the SC cache. The new procedures substantially and transparently improve the combined caching efficiency without significant new hardware or software overhead.

Management system for a hierarchical data cache employing preemptive

A method and system for enhancing the efficiency of communication between multiple direct access storage devices and a storage system controller in a data processing system. In a data processing system having a storage system controller connected between a plurality of host computers and a plurality of storage devices, a processors, within the storage system controller, is provided for controlling the storage devices. Commands and data are communicated between the processor and the storage devices over a communication channel. An independent polling mechanism is provided which is coupled to the communication channel and the processor. The independent polling mechanism is utilized for collecting and storing interrupt status data from each of the storage devices. An interrupt circuit coupled to the independent polling mechanism is then utilized to produce an interrupt signal at the processor, in response to the state of the interrupt status data collected from the storage devices, wherein the polling of the storage devices by the processor is not required. By utilizing an independent polling mechanism the manner in which the storage devices are polled may be selectively controlled such that only selected storage devices are polled, only selected interrupt status conditions are recognized, or periodic interrupt signals are generated regardless of the status of the storage devices.

Method and system for enhancing the efficiency of communication between

A method and system for enhancing the efficiency of data accessing within a storage subsystem which is coupled to a host system via a storage subsystem controller and a data channel. The storage subsystem controller preferably includes a tracked cyclic storage device which has multiple disks which are rotatable about a single spindle. Recording tracks within each disk are then accessed utilizing multiple switchable transducer heads. A signal transmitted from the host system is utilized to define a sequence in which a group of recording tracks are to be accessed. That signal is then utilized to create a transducer head switching table within the storage subsystem controller which lists each recording track to be accessed and an associated control parameter for selecting a particular transducer head to be utilized to access a subsequent recording track. Each time the end of an accessed recording track is encountered, the transducer head switching table is accessed and the control parameter associated with that track is accessed and coupled to the tracked cyclic storage device transducer head switch in order to select a subsequent recording track for access. In this manner, a plurality of tracks may be accessed in any desired order. A pointer is established into the transducer head switching table at the listing of an initially accessed recording track and access may be terminated when that pointer is encountered.

Method and system for accessing data from a multi-head data processing

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Tucson, AZ, United States of America

William G Sherman, Ii