Abstract: A technique for determining an optimal number of tasks for processing requests is provided. It is determined whether there are one or more first requests that have not been processed. A parallelism assessment is performed for simulating the assignment of said first requests to one or more task representations.

Abstract: In a data storage system with multiple output media types, each request to store a data object is automatically analyzed to select the optimal output media type. In choosing the output media type best suited to quickly and efficiently complete the storage requests, the storage system considers (1) attributes of the data object itself, such as its size, (2) any perceived urgency required to complete the data storage request, and (3) attributes of the system's storage devices, such as the availability of different output media types, presence of other storage requests queued for storage for each type, level of ongoing access of each storage type by concurrent storage tasks, delays to initiate storage such as mount/demount times, amount of storage space available in different output media types, and the like.

Abstract: In a computing system with non-shareable resources, use-arbitrating processes are executed on behalf of each task seeking or having access to non-shareable resource. The processes compete according to prescribed rules and priority guidelines, the resolution of which determines access to the non-shareable resource. If application of the priority guidelines permits, a use-requesting task can institute takeaway of a resource from a task that is already using the resource.

Abstract: In a data storage system that employs multiple storage drives to access removable data storage media, idle data storage media are analyzed and than selectively demounted by automated equipment to increase storage drive availability and also minimize unnecessary mount/demount operations. Initially, the system establishes a maximum permitted number of concurrently mounted idle storage media, and also establishes a maximum permitted length of time for leaving idle storage media mounted. Next, storage media mounted to the media drives are analyzed for possible demounting. The system determines how many storage media are presently mounted, and each media's mount time. Then, the system identifies suitable demounting candidates (if any) to comply with the established maximums.

Abstract: A data management system responds to migration requests by automatically invoking a shortcut migration process for suitable candidates. Suitability of candidate data is efficiently evaluated using, among other considerations, the presence or absence of an expedited access indicator for the data which is previously set when the data is recalled from backup storage. In the shortcut migration process, the system automatically reconnects a previously migrated copy of the data object, if available.

Abstract: Disclosed is a system for handling recall requests for data maintained in storage devices from a host system. The host system maintains a queue of recall requests to a plurality of storage devices. Priority data is associated with each recall request in the queue. The host system initiates a recall operation for a recall request in the queue to a first storage device mounted in a drive. The host system then determines whether a next recall request to the first storage device has a higher priority than a recall request to a second storage device not mounted in a drive. The recall operation for the next recall request to the first storage device is performed after determining that the next recall request has the higher priority. The first storage device is demounted from the drive after determining that the recall request to the second storage device has the higher priority. The second storage device to the drive is mounted after demounting the first storage device from the drive.

Abstract: Disclosed is a system for handling recall requests for data maintained in a storage device accessible to multiple systems. Initially, a storage device is allocated to the first host system to process recall requests in a recall queue including a plurality of recall requests. A second host recall request is initiated with the second host system to recall data from the storage device. The second host system determines whether the storage device is allocated to the first host system. If so, the second host systems stores priority data in a common or shared data structure indicating a priority of the second host recall request after determining that the storage device is allocated to the first host system. The first host system then conditionally releases the storage device before processing all the recall requests needing the subject tape in its queue to make the storage device available if the priority in the common data structure is higher than its own highest priority request.

Abstract: A system and method for increasing capacity utilization of non-volatile storage devices within a group of non-volatile storage devices used to store data from at least one attached system are disclosed. A group of data sets is written to a first storage device as part of a write operation such as migration. A plurality of storage devices partially filled with data are designated as substitutes. The write operation to the first storage device is suspended upon receiving a request to read a data set stored in the first storage device, such as occurs in a recall operation. A second storage device is then selected from the plurality of substitute storage devices. The write operation is continued by writing data sets from the group of data sets included in the write operation that were not written to the first storage device to the selected second storage device. The requested data is then read from the first storage device.

Abstract: A data processing system includes a data storage subsystem containing a plurality of data storage devices for reading and writing data on a plurality of data storage volumes. The data processing system is controlled by software to perform a method for recycling the data storage volumes containing a percentage of still valid data and a percentage of invalid data by transferring the still valid data on a plurality of input data storage volumes to one or more output data storage volumes. In accordance with the recycling method, the data processing system assigns a selected number of the data storage devices as input devices and a selected number of the data storage devices as output devices in a predetermined input/output ratio of the form m:k, where m is the number of input devices and k is the number of output devices. The system then commences transferring still valid data from input volumes mounted on the input devices to output volumes mounted on the output devices.

Abstract: A system for recovering multi-volume data sets that are stored in one or more volumes that have failed with a substantial level of automation and flexibility. Data can be recovered from backup storage when multiple volumes fail, as in a "catastrophic" data loss. For each volume, all data sets partially or completely stored on the selected volume prior to a failure of that volume are identified. Each single-volume data set stored on the selected volume prior to the failure is restored from backup storage. Upon identifying a multi-volume data set whose beginning segment was stored on the selected volume, the entire data set is restored. Data can also be recovered from backup storage when a particular volume fails, such as after a "head crash." All data sets partially or completely stored on the selected volume prior to a failure of that volume are identified. Each single volume data set stored on the selected volume prior to the failure is recovered from backup storage.