Abstract: An apparatus and method for disk mapping and data retrieval includes a data storage medium on which has been stored a plurality of data records. Each record includes at least a record identification portion, for uniquely identifying each record from among the plurality of data records. The apparatus builds a record locator table in high speed semiconductor memory which comprises the unique record identifiers for the records on the storage medium as well as a record locator index generated by the apparatus, which indicates the address of the data record on the storage medium. Data retrieval is facilitated by first searching the record locator table in high speed semiconductor memory for a requested data record. Utilizing the record locator index associated with the requested data record, the system directly H: accesses the requested data record on the storage medium thereby minimizing storage medium search time.

Abstract: A system and method for providing on-line, real-time, transparent data migration from an existing storage device to a replacement storage device. The existing and replacement storage devices are connected as a composite storage device that is coupled to a host, network or other data processing system. The replacement storage device includes a table which identifies data elements that have migrated to the replacement storage device. When a host system makes a data transfer request for one or more data elements, the replacement storage device determines whether the data elements have been migrated. If the data elements have migrated, the replacement storage device responds to the data transfer request independently of any interaction with the existing storage device. If the data elements have not migrated, the replacement storage device migrates the requested data elements and then responds to the data request and updates the data element map or table.

Abstract: A system and method for providing on-line, real-time, transparent data migration from an existing storage device to a replacement storage device. The existing and replacement storage devices are connected as a composite storage device that is coupled to a host, network or other data processing system. The replacement storage device includes a table which identifies data elements that have migrated to the replacement storage device. When a host system makes a data transfer request for one or more data elements, the replacement storage device determines whether the data elements have been migrated. If the data elements have migrated, the replacement storage device responds to the data transfer request independently of any interaction with the existing storage device. If the data elements have not migrated, the replacement storage device migrates the requested data elements and then responds to the data request and updates the data element map or table.

Abstract: A method and apparatus for interfacing two ESCON compatible devices over a communication channel that is not dedicated solely to ESCON communication, such as a public communication network or links, for example, a T1 or T3 line. The devices may include a master storage device and a mirroring storage device disposed at remote locations. In one embodiment, the devices communicate using the ESCON protocol.

Abstract: A system and method for providing on-line, real-time, transparent data migration from an existing storage device to a replacement storage device. The existing and replacement storage devices are connected as a composite storage device that is coupled to a host, network or other data processing system. The replacement storage device includes a table which identifies data elements that have migrated to the replacement storage device. When a host system makes a data transfer request for one or more data elements, the replacement storage device determines whether the data elements have been migrated. If the data elements have migrated, the replacement storage device responds to the data transfer request independently of any interaction with the existing storage device. If the data elements have not migrated, the replacement storage device migrates the requested data elements and then responds to the data request and updates the data element map or table.

Abstract: A system and method for providing on-line, real-time, transparent data migration from an existing storage device to a replacement storage device. The existing and replacement storage devices are connected as a composite storage device that is coupled to a host, network or other data processing system. The replacement storage device includes a table which identifies data elements that have migrated to the replacement storage device. When a host system makes a data transfer request for one or more data elements, the replacement storage device determines whether the data elements have been migrated. If the data elements have migrated, the replacement storage device responds to the data transfer request independently of any interaction with the existing storage device. If the data elements have not migrated, the replacement storage device migrates the requested data elements and then responds to the data request and updates the data element map or table.

Abstract: An apparatus and method for disk mapping and data retrieval includes a data storage medium on which has been stored a plurality of data records. Each record includes at least a record identification portion, for uniquely identifying each record from among the plurality of data records. The apparatus builds a record locator table in high speed semiconductor memory which comprises the unique record identifiers for the records on the storage medium as well as a record locator index generated by the apparatus, which indicates the address of the data record on the storage medium. Data retrieval is facilitated by first searching the record locator table in high speed semiconductor memory for a requested data record. Utilizing the record locator index associated with the requested data record, the system directly accesses the requested data record on the storage medium thereby minimizing storage medium search time.

Abstract: Two data storage systems are interconnected by a data link for remote mirroring of data. Each volume of data is configured as local, primary in a remotely mirrored volume pair, or secondary in a remotely mirrored volume pair. Normally, a host computer directly accesses either a local or a primary volume, and data written to a primary volume is automatically sent over the link to a corresponding secondary volume. Each remotely mirrored volume pair can operate in a selected synchronization mode including synchronous, semi-synchronous, adaptive copy-remote write pending, and adaptive copy-disk. Direct write access to a secondary volume is denied if a “sync required” attribute is set for the volume and the volume is not synchronized. If a “volume domino” mode is enabled for a remotely mirrored volume pair, access to a volume of the pair is denied when the other volume is inaccessible.

Abstract: A system and method for providing on-line, real-time, transparent data migration from an existing storage device to a replacement storage device. The existing and replacement storage devices are connected as a composite storage device that is coupled to a host, network or other data processing system. The replacement storage device includes a table which identifies data elements that have migrated to the replacement storage device. When a host system makes a data transfer request for one or more data elements, the replacement storage device determines whether the data elements have been migrated. If the data elements have migrated, the replacement storage device responds to the data transfer request independently of any interaction with the existing storage device. If the data elements have not migrated, the replacement storage device migrates the requested data elements and then responds to the data request and updates the data element map or table.

Abstract: A cache management system and method monitors and controls the contents of cache memory coupled to at least one host and at least one data storage device. A cache indexer maintains a current index of data elements which are stored in cache memory. A sequential data access indicator, responsive to the cache index and to a user selectable sequential data access threshold, determines that a sequential data access is in progress for a given process and provides an indication of the same. The system and method allocate a micro-cache memory to any process performing a sequential data access. In response to the indication of a sequential data access in progress and to a user selectable maximum number of data elements to be prefetched, a data retrieval requestor requests retrieval of up to the selected maximum number of data elements from a data storage device. A user selectable number of sequential data elements determines when previously used micro-cache memory locations will be overwritten.

Abstract: An apparatus and method for disk mapping and data retrieval includes a data storage medium on which has been stored a plurality of data records. Each record includes at least a record identification portion, for uniquely identifying each record from among the plurality of data records. The apparatus builds a record locator table in high speed semiconductor memory which comprises the unique record identifiers for the records on the storage medium as well as a record locator index generated by the apparatus, which indicates the address of the data record on the storage medium. Data retrieval is facilitated by first searching the record locator table in high speed semiconductor memory for a requested data record. Utilizing the record locator index associated with the reqested data record, the system directly accesses the requested data record on the storage medium thereby minimizing storage medium search time.

Abstract: Two data storage systems are interconnected by a data link for remote mirroring of data. Each volume of data is configured as local, primary in a remotely mirrored volume pair, or secondary in a remotely mirrored volume pair. Normally, a host computer directly accesses either a local or a primary volume, and data written to a primary volume is automatically sent over the link to a corresponding secondary volume. Each remotely mirrored volume pair can operate in a selected synchronization mode including synchronous, semi-synchronous, adaptive copy - remote write pending, and adaptive copy - disk. Direct write access to a secondary volume is denied if a "sync required" attribute is set for the volume and the volume is not synchronized. If a "volume domino" mode is enabled for a remotely mirrored volume pair, access to a volume of the pair is denied when the other volume is inaccessible.

Abstract: A dual bus architecture for a computer system including a number of computer system devices and a number of computer system resources. Each of the computer system devices and computer system resources are coupled by first and second communication busses. First and second bus arbitrators provide bus arbitration functions allowing first and second computer system devices to access first and second computer system resources simultaneously. A method of accessing a number of computer system resources by a number of computer system devices coupled by a dual bus architecture is also provided.

Abstract: A system and method for providing on-line, real-time, transparent data migration from a first data storage system to a second data storage system. The first data storage system which had previously been coupled to a host, network or other data processing system is disconnected from the host and connected to a second data storage system. The second data storage system is coupled to the host or data processing system. The second data processing system includes a data map or table which indicates which data elements are stored on the second data storage system and which corresponding data elements on the first data processing device have been copied to the second data storage system. When the host, network or data processing system requests data from a data storage system, the second data storage system determines whether or not the data is stored on the second or first data storage system. If the data is stored on the second data storage system, the data is made available to the requesting device.

Abstract: An apparatus and method for disk mapping and data retrieval includes a data storage medium on which has been stored a plurality of data records. Each record includes at least a record identification portion, for uniquely identifying each record from among the plurality of data records. The apparatus builds a record locator table or high speed semiconductor memory which comprises the unique record identifiers for the records on the storage medium as well as a record locator index generated by the apparatus, which indicates the address of the data record on the storage medium. Data retrieval is facilitated by first searching the record locator table in high speed semiconductor memory for a requested data record. Utilizing the record locator index associated with the requested data record, the system directly accesses the requested data record on the storage medium thereby minimizing storage medium search time.

Abstract: A color separation scanner comprising a support arranged for mounting thereon of a two-dimensional image to be scanned and color separation sensing apparatus arranged for sensing the two-dimensional image. The color separation apparatus includes a scanning head located a fixed distance from the two-dimensional image, at least first and second objective lens assemblies and apparatus for selectively arranging each of the at least first and second objective lens assemblies in fixed locations along the optical path between the image and the scanning head.

Abstract: A data storage system which automatically provides and maintains identical secondary data on a preferably geographically remote secondary data storage device. The system includes a primary host computer located in the first geographic location which is coupled to a primary data storage system also located in the first geographic location. The primary data storage system includes at least one primary data storage device on which primary data is to be stored, and a primary data storage system controller which receives data from the primary host computer and controls the storing of the primary data on the primary data storage device.

Abstract: A cache management system and method monitors and controls the contents of cache memory coupled to at least one host and at least one data storage device. A cache indexer maintains a current index of data elements which are stored in cache memory. A sequential data access indicator, responsive to the cache index and to a user selectable sequential data access threshold, determines that a sequential data access is in progress for a given process and provides an indication of the same. The system and method allocate a micro-cache memory to any process performing a sequential data access. In response to the indication of a sequential data access in progress and to a user selectable maximum number of data elements to be prefetched, a data retrieval requestor requests retrieval of up to the selected maximum number of data elements from a data storage device. A user selectable number of sequential data elements determines when previously used micro-cache memory locations will be overwritten.

Abstract: A data storage system with data mirroring and reduced access time data retrieval includes at least one pair of rotating data storage media each having a plurality of generally identical data records. Each rotating data storage medium includes position indicators, for providing one or more indications of the rotational position of each of the rotating data storage media with respect to its associated fixed position read/write mechanism. A position monitor receives the rotational position indications from each rotating data storage medium and computes and monitors the rotational position of each rotating storage medium with respect to its associated read/write mechanism.

Abstract: A cache management system and method monitors and controls the contents of cache memory coupled to at least one host and at least one data storage device. A cache indexer maintains a current index of data elements which are stored in cache memory. A sequential data access indicator, responsive to the cache index and to a user selectable sequential data access threshold, determines that a sequential data access is in progress for a given process and provides an indication of the same. The system and method allocate a micro-cache memory to any process performing a sequential data access. In response to the indication of a sequential data access in progress and to a user selectable maximum number of data elements to be prefetched, a data retrieval requestor requests retrieval of up to the selected maximum number of data elements from a data storage device. A user selectable number of sequential data elements determines when previously used micro-cache memory locations will be overwritten.