Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.