Abstract: A method and system are provided for improving the speed for writing data in a disk array system (RAID). Sectors of the disks are divided into the ones for reading old data and the other ones for writing new data. An external semiconductor storage device is used as a parity device which significantly enhances performance in writing. Preferably, a disk array system is used for storing data for which a parity group comprises N data units stored in sectors of N magnetic disk drives with parity stored in the parity device. At least N+1 magnetic disk drives are provided, where sectors of at least one magnetic disk drive are used as redundant sectors.

Abstract: A system and method are provided for preserving spacial and temporal locality of sets of related objects when moving the sets within a storage hierarchy via a common server. The appropriate meta data is gathered to track the spacial and temporal locality of the sets of objects being moved within the storage hierarchy and the algorithm uses the meta data to preserve the spacial and temporal locality when moving the objects. A collection of logically clustered data objects is identified. The logical cluster is then moved down through the storage hierarchy together to be stored in less costly storage devices. The logical cluster of data objects is then retrievable more efficiently as a whole when requested.

Abstract: A system and method are provided for sharing a data stream between a first data storage system in communication with a second data storage system. Meta-data is associated with each record of the data stream. Zero or more records of the data stream are compressed at the first storage system. The meta-data for the compressed data record is updated to indicate that the data record has been compressed. The data stream including the compressed data record with the updated meta-data is sent to the second storage system. The meta-data and the data stream records are stored on a storage device at the second data storage system.

Abstract: Distributed data processing systems with replication of data across the system are required to provide data access and availability performance approaching that of a stand-alone system with its own data, but reductions in network traffic gained by replication must be balanced against the additional network traffic required to update multiple copies of the data. Apparatus and a method of operating a distributed data processing system is provided in which a currency period is associated with each copy of a data object and the data object is assumed to be valid during the currency period. The apparatus has means for checking (500) whether the currency period has expired and means for updating (570, 580) the copies. A validity indicator is set on determination of expiry of the currency period and when updates are applied to the primary copy, and is checked to determine validity of a copy.

Abstract: A data processing system and method providing error protection for data transmitted between a processor and a buffer in one data format and transmitted between the buffer and a user device in a different data format. An adaptor is interposed between the processor and the buffer for transmitting to the buffer (i) successive data segments in the one data format, each ending with appended check bytes in a preselected cyclic redundancy code (CRC); and (ii) check bytes using the same CRC appended at the end of each segment in the different data format to create in the buffer records which are a composite of both formats, but viewed as in the one data format by the processor and as in the different data format by the user device. The boundaries of the segments in each format must be known to the adaptor. Since both formats use the same CRC, CRC bytes for each segment in each data format will provide an identical preselected value in the absence of a detectable error.

Abstract: A cache system is described which is adapted for staging data between host memory and a disk array comprising a plurality of disk storage devices plus associated controller unit, data being storable across the disks of the array in the form of strides, each stride comprising a multi-sector `stripe` of data on each of two or more devices of the array and an associated multi-sector parity block on a further array device. The cache system includes means for linking the data and associated parity making up a stride within the cache as a cache data unit which is manipulated in the cache as a single entity. References from the host to data held within the cache causes the referenced cache unit to move to the head of a list of cache units.

Abstract: Some disk drives produce a relatively large amount of acoustical noise. This noise is generated by vibrations of the disk drive cover caused by movement of the spindle motor and/or actuator head. A disk drive assembly is provided that significantly reduces the amount of acoustic noise emanating from a disk drive. An enclosure for a disk stack assembly, comprising at least one disk, mounted on a spindle attached to a motor and an actuator assembly, comprising at least one head attached to an actuator, is provided. The enclosure has an inner chamber with a post extending outwardly from a surface of the inner chamber. A compressible material is disposed at one end of the post abutting in a compressed state an opposing surface of the inner chamber. In a preferred embodiment, the post is integrally formed with the inner chamber and is unattached from the opposing surface. The damping post is preferably positioned in a position of maximum deflection for the vibration mode of the assembly.

Abstract: A backup method for a computer database system comprising maintaining a mirrored copy of the database at a remote location is characterized in that updates to the remote database data are delayed for a delay time greater than or equal to the upper limit on the data communication delay between the local location and the remote location and updates to a remote log for the database are executed after corresponding updates to a local log without said delay. In this way a consistent copy of the database may be recovered from the mirrored copy of the database and the remote log after destruction of the database system.

Abstract: When an update is made to a data record in a distributed, replicated data processing system, the update is first applied to a primary copy of the data record before being applied to any other copy to ensure that updates are applied in the correct time sequence. Apparatus and a method of operating a distributed data processing system is provided in which responsibility for the primary copy is transferable to whichever processor in the system requires most frequent update access, providing improved performance and availability of data. The primary copy may be partitioned and distributed across the system.

Abstract: A system and method are provided that is used by software implemented Redundancy Array of Inexpensive Disk (RAID) arrays to achieve adequate performance and reliability, as well as to improve performance or low cost hardware Raids. The enhancements to the basic RAID implementation speeds up recovery time for software RAIDS. A method is provided for storing data in an array of storage devices. A plurality of block locations on the storage devices are logically arranged as a parity group wherein a parity block stored in a block location as part of a parity group is logically derived from the combination of data blocks stored in the parity group, and each block in a parity group is stored on a different storage device. A plurality of parity groups are grouped into a parity group set. A request is received to write a new data block location on a storage device. The old data block stored at the block location is read. The new data block is written to the block location.

Abstract: A new format of executable program is provided which is flexible and open-ended to provide a means for storing heterogeneous program data in an executable program. In a computer system having a central processing unit, memory, and a storage device, a system and method of executing a computer program is provided for converting one or more source programs into an executable program. The data from the object modules are arranged according to a set of predefined classes. Each class of data is written out to memory keeping data from the same class stored together. Only the data in classes needed for running the program are loaded into memory. As data is required to continue running the program, it is read into memory. A directory is maintained of where each class is stored on the storage device.

Abstract: A method for avoiding a cache-full condition in an LRU organized, data set partitioned, page oriented cache of a defined capacity intercoupling a processor to an external storage subsystem is provided. The processor is capable of storing pages of a data set into a plurality of cache partitions. The method comprises the steps of periodically determining the target size of each partition for optimal partitioning, and assigning a reclaim vector to each partition specifying the number of frames to be stolen from each of the other partitions necessary to achieve the corresponding target size. If the target size of a particular partition is less than the partition's virtual minimum size, the method adjusts that partition's reclaim vector to enable the partition to steal sufficient frames from other partitions to achieve the virtual minimum size.

Abstract: A method and system are provided for controlling the access to objects in an object oriented data processing application, where the objects are being hierarchically structured and either locally available or retrievable from an external unit. Each object has a dependent object counter which indicates the existence or the number of dependent objects associated with that object. When at least one dependent object is not locally available, a dummy object is appended to that object, enabling the object expansion even if the dependent objects of the selected object are not yet locally available in local memory. The objects to be retrieved from the external unit are locked from user access, while access is allowed to the locally available dependent objects.

Abstract: A method of removing uncommitted changes made to stored data by a database management system, wherein the system stores a duplicate copy of data prior to effecting changes to the original copy, and upon failure of the system or of a transaction or transactions effecting the changes, replaces the copy containing uncommitted changes by the duplicate copy. If the system fails to replace the original copy (as in the case of a backout failure), the system prevents subsequent attempts by the system to further change the data until the uncommitted changes have been removed by a process of backout failure processing. Backout failure log records are created to track whether the system completed its backout failure processing (END), which transactions had failed backout (SUBSEQUENT), and which transaction was the first to have a backout failure (FIRST). A batch backout utility program uses the set of backout failure log records to bracket the duration of the backout failure for a particular file.

Abstract: In a computer database system, a method and system are provided for interactively and iteratively constructing a query using a table metaphor displayed on a user display. Alterations are made directly to the table metaphor by the database user. The alterations relate to adding, deleting, or combining columns of attributes and limiting ranges of attribute values. The alterations are registered and the table metaphor updated to reflect the registered alterations. The table metaphor can be repeatedly used to further register additional alterations. The query corresponding to the table metaphor in its final form is run against the full database to generate a report in the format indicated by the table metaphor.

Abstract: A data storage system is described which provides for fault tolerance during execution of a media maintenance program on a selected track of nonvolatile data storage. Checkpoint data for the media maintenance program is stored in nonvolatile storage prior to writing control information on the selected track during the execution of the media maintenance program. The checkpoint data includes an address in the media maintenance program for resuming execution in the event that the media maintenance process is aborted. The checkpoint data is read from the nonvolatile storage area after media maintenance has been aborted by a fault, typically after power has been reapplied to the system. The execution environment for the media maintenance program is restored by storing data in the RAM of the controller which duplicates the control data needed by the particular segment of the media maintenance program which will be restarted.

Abstract: A computer token identification system uses a plurality of unique tokens to represent a plurality of items. The token architecture consists of a delimiter field, a version field, and a variable field. The delimiter field contains at least one token recognition character. The version field immediately follows the delimiter field and contains the version string of at least one character identifying a unique token version. The variable field immediately follows the version field and contains a variable string of at least one character conforming to a format specification for the token version. Each variable string is unique for a token version. The version string and variable string can be of varying lengths, and the characters of the version string and variable string that are adjacent are from different character set types.

Abstract: An automated method is provided for optimizing a query for retrieving data from a relational database in a computer relational database management system. The method uses rules for identifying queries for which duplicates are a factor in retrieving the proper data from the database. The method then merges queries with table expressions, views and subqueries when possible without causing duplicates to be unnecessarily retrieved.

Abstract: A method for accessing a stored data base comprising a number of blocks, each of said blocks containing a plurality of data files and a directory with access keys of the files stored in each of the respective blocks, and comprising means for effecting a sorted ordering of the data files such that the access keys in each block have a predetermined relation. Before the data base is accessed the directories of all blocks are read once in a predetermined order to determine the range of access keys in each directory. Thereafter, during each access operation first of all those directories are sorted out (identified) in which, based on the determined ranges of access keys, the search key of the requested data file might be present. Only blocks corresponding to the sorted out directories are then searched for the requested data file.