Abstract: A method for enabling overlapped input/output requests to a logical device using assigned and parallel access unit control blocks. Each I/O request interrupts an operating system to assign a base and related unit control block to the input/output requests. In addition a parallel access control block is associated with each unit control block for a logical volume and a parallel access main control block is established with a logical volume through which each of the base and related unit control block can be identified. An input/output request to a logical device interrupts the operating system to assign one of the base and one of the assigned unit control blocks to the input/output requests after which control transfers back to the operating system. At a disk storage facility, the input/output request is located in a table with other input/output requests and corresponding parameters.

Abstract: A method for enabling for enabling overlapped input-output request to a logical device from multiple hosts with explicit allegiances. Parameters including an address range in a new input-output request are tested against corresponding address ranges in other input-output requests in a table assigned to the logical device. If a predetermined address range relationship exits, the new input-output guest transfers to an overlap polling queue.

Abstract: A scheduler for selecting a logical volume for job generation based on the loading of physical resources in a data storage system. The scheduler determines a job workload for each of the physical resources, selects physical resources based on the job workload and selects a logical volume supported by the selected physical resources in a balanced manner.

Abstract: A primary data storage system is linked to a geographically remote secondary data storage system for automatically maintaining a remote copy of the data in the primary storage. The primary data storage system controller uses write pending indicators to control and coordinate the remote copy process. In response to receipt of data from the host computer, a first write pending indicator is set to write the data into at least one primary data storage device, and a second write pending indicator is set to copy the data to the secondary data storage system controller. The first write pending indicator is reset after the data is written to the primary data storage device, and the second write pending indicator is reset after receiving an acknowledgement back from the secondary data storage system controller.

Abstract: Accessing data includes a host establishing a relationship between a first storage area of a first type containing data and a second storage area of a second type containing pointers to data provided in storage areas of the first type, where the storage areas are provided in a storage device coupled to the host. In response to the host writing data to a particular section of the first storage area after establishing the relationship, the particular section is copied from the first storage area to a third storage area of the first type prior to the write operation being executed. A corresponding pointer of the second storage area is adjusted to point to the third storage area.

Abstract: Restoring data includes providing data in a first storage area that contains sections of data, providing data in a second storage area where the second type has, for each section of data thereof, at least one of: a pointer to a corresponding section of data of the first storage area and a pointer to corresponding section of data of a third storage area of the first type. In one embodiment, a sections of the first storage area are replaced with pointers to the third storage area. In other embodiments, sections of a fourth storage area of the first type are replaced with pointers to the third storage area and optionally with pointers to the first storage area. In another embodiment, data is copied from the second storage area to a third storage area of the second type.

Abstract: Establishing a plurality of storage areas includes associating each of a first plurality of storage areas of a first type that contain sections of data with corresponding ones of second plurality of storage areas of a second type having pointers to alternative sections of data storage areas of the first type, where initially none of the second plurality of storage areas is available for accessing data corresponding thereto, and, after associating all of the first and second plurality of storage areas, activating the second plurality of storage areas to make the second plurality of storage areas available for accessing data. Exclusive access may be enabled for all of the first plurality of storage areas prior to activating the second plurality of storage areas or to each storage area one at a time.

Abstract: Accessing stored data includes providing a virtual storage area having a table of pointers that point to sections of at least two other storage areas, where the virtual storage area contains no sections of data, in response to a request for accessing data of the virtual storage area, determining which particular one of the other storage areas contain the data, and accessing the data on the particular one of the other storage areas using the table of pointers. Accessing stored data may also include associating a first one of the other storage areas with the virtual storage area, where the virtual area device represents a copy of data of the first one of the other storage areas. Accessing stored data may also include causing all of the pointers of the table to initially point to sections of the first one of the other storage areas when the virtual storage area is initially associated with the first one of the other storage areas. The storage areas may be storage devices. The sections may be tracks.

Abstract: Handling data includes providing a first storage area of a first type that contains sections of data, providing a second storage area of the first type that contains sections of data, providing a third storage area of a second type where the second type has, for each section thereof, a pointer to one of: a corresponding section of data of the first storage area and a corresponding section of data of the second storage area, causing the third storage area to be not available for accessing, and after causing the third storage area to not be available for accessing, providing data from the second storage area corresponding to pointers of the third storage area that point to sections of the second storage area.

Abstract: A method for enhancing the performance of an application on a data processing system that operates with a disk array storage device in which the completion of tasks associated with different transactions with one logical storage device are conditions precedent to the completion of other transactions. Specific tasks related to the one logical device are given priority over tasks related to all other logical storage devices. In a specific implementation reconnect tasks are given the highest priority with reconnect tasks from the one logical storage device being given the highest priority. A second category of tasks related to the one logical storage device can be given priority over all other tasks except reconnect tasks. All other tasks are given a priority below that of the first and second task categories.

Abstract: A digital data storage system in the form of a mass storage subsystem in which information is stored on one or more disk storage units, with a storage element constituting a track on a disk storage device and each track storing a plurality of records. Each track in each disk storage device of the digital data storage system is associated with a descriptor. When the control device retrieves the contents of a record, it can process the contents to generate a check value and compare the generated check value with the check value for the record as stored in the descriptor associated with the track. If they compare appropriately, the control device can determine that the record that was retrieved was, in fact, the record that was to be retrieved. On the other hand, if they do not compare appropriately, the control device can determine that the record that was retrieved was not the proper record.

Abstract: A method and apparatus for enabling an on-line reconfiguration of striped data in a disk array storage device. A replicated copy of the striped logical device is made in parallel with host operations. A logical device with a new configuration is then substituted for access by the host application even before any data is transferred to locations within the newly configured logical device. Independent processes operating in this disk array storage device reconfigure the data transparently to any host operations while accommodating host I/O requests directed to locations in the new configuration.

Abstract: A primary data storage system is linked to a geographically remote secondary data storage system for automatically maintaining a remote copy of the data in the primary storage. Each of the data storage systems has at least one data storage device, a cache memory, a data storage system controller, and a service processor for servicing the data storage system. The primary and secondary service processors are linked to permit remote system configuration and remote software programming of the secondary data storage system, and to exchange a report of all the non-valid, out of sync tracks. The service processors can also perform the task of scanning for remote write pending bits to invoke the remote copy task, and checking for invalid track bits to invoke a task for copying data from a known good storage device to the device with the invalid track bit set.

Abstract: A primary data storage system is linked to a geographically remote secondary data storage system for automatically maintaining a remote copy of the data in the primary storage. The primary data storage system has a primary cache memory, and the secondary data storage system has a secondary cache memory. The primary data storage system controller has a first remote link adapter coupled between the primary cache memory and the communications link for transferring the data to the communications link. The secondary data storage system controller has a second remote link adapter coupled between the communications link and the secondary cache memory for transferring the data from the communications link to the secondary cache memory. In this fashion, the first remote link adapter and the second remote link adapter automatically transfer the data to the secondary cache memory for writing of the data into the secondary data storage.

Abstract: A digital data storage system comprises a storage device, a descriptor memory and a control device. The storage device stores a series of records, the records being organized in a plurality of tracks, each track being associated with one of a plurality of cylinders. The descriptor memory stores a descriptor associated with storage device. The descriptor contains selected information relating to the records stored by the at least one storage device. Each descriptor includes a plurality of cylinder portions each configured to store selected information relating to a respective one of the cylinders in the storage device. Each cylinder portion, in turn, includes a plurality of track descriptors each configured to store selected information relating to a respective one of the tracks in the respective cylinder. The storage device also stores the descriptor associated therewith, the cylinder portions of the descriptor being augmented with additional information relating to the respective ones of the cylinders.

Abstract: Managing data in cache includes providing data from a disk storage area to a first cache memory, providing data from the disk storage area to a second cache memory, where the first and second cache memories contain at least some data that is not stored in the other one of the cache memories, and writing the same data to both of the cache memories in response to the data being modified while stored in the cache memories. Managing data in a cache may also include subdividing the first cache memory into primary and secondary storage areas, subdividing the second cache memory into primary and secondary storage areas, where primary areas of the first cache correspond to secondary areas of the second cache and where secondary areas of the first cache correspond to primary areas of the second cache, and providing data from the disk storage area to the one of the cache memories having a corresponding primary storage area.

Abstract: A data storage system includes data storage and a record locator data structure in random access memory. The record locator data structure includes entries having different lengths. For locating variable-length data records in the data storage, for example, at least some but not all of the entries have a data-length portion indicating data length of a respective data record of the entry when the data length of the respective data record fails to match an expected data length. Each entry, for example, has a fixed length portion including an indication of whether or not the entry has a data-length portion, the fixed length portions are stored sequentially in a first region of address locations of the random access memory, and the data-length portions are stored sequentially in a second region of address locations of the random access memory.

Abstract: A method and apparatus for enabling an on-line reconfiguration of striped data in a disk array storage device. A replicated copy of the striped logical device is made in parallel with host operations. A logical device with a new configuration is then substituted for access by the host application even before any data is transferred to locations within the newly configured logical device. Independent processes operating in this disk array storage device reconfigure the data transparently to any host operations while accommodating host I/O requests directed to locations in the new configuration.

Abstract: A method and apparatus for enabling a common data set to be utilized by multiple data processes. During a first operating mode, first and second data stores in a data storage facility with a common buffer attach to a first data process and act as mirrors. Data to be written transfers to the common buffer and then to the data stores. A second command produces a split whereby the first data store remains attached to the first data process and the second data store is available to the second data process. After the second command is executed, any data in the common buffer is transferred to the corresponding data stores in parallel with and transparently to the actions between the first and second data processes and the first and second data stores, respectively.

Abstract: A primary data storage system is linked to a geographically remote secondary data storage system for automatically maintaining a remote copy of the data in the primary storage. The primary data storage system controller uses write pending indicators to control and coordinate the remote copy process. In response to receipt of data from the host computer, a first write pending indicator is set to write the data into at least one primary data storage device, and a second write pending indicator is set to copy the data to the secondary data storage system controller. The first write pending indicator is reset after the data is written to the primary data storage device, and the second write pending indicator is reset after receiving an acknowledgement back from the secondary data storage system controller.