Abstract: A method is described for encoding and decoding stored units of data representing entity/relationship (E/R) data, function calls, and file data by including a prefix with each unit of data which includes a length code, an action code, and a unit identifier code. The data units with prefixes are organized into a data stream by using rules described in a formal grammar. The data stream will typically be transmitted to another program inside the computer or to another computer--host or PWS. When received the data stream is parsed back into data units by reversing the encoding process. After the data units are recovered the appropriate action is taken to process the units. E/R data is entered into or updated in a repository, function calls are passed on to an E/R repository function or other program along with the specified parameters for execution, and file data is stored in standard files.

Abstract: A method for maintaining switchover between a backup and degrading active processor, which switchover is transparent to a terminal accessing the active processor with atomic transactions. The backup processor prepares for an outage by the active processor by synchronizing, tracking, and monitoring the active processor's log entries. When the active processor fails, the backup processor performs the necessary recovery processing and takes over user-transactions processing as the new active processor.

Abstract: This invention measures the degree of clustering of an index for a relational data base table, estimates the number of physical page accesses required to access the table using a partial index scan using the index, and selects the index providing the fastest access path to the table. The degree of clustering is measured as follows:DC=Number of clustered rows (NCR)/Total rows (NR)A multiplier greater than 1 can be applied to the degree of clustering to reflect the benefit of having consecutively accessed rows on adjacent or nearby data pages.The degree of clustering so calculated is used to estimate the number of random and sequential page accesses required for a partial index scan. These numbers of accesses are then multiplied by the unit time required for each, and added to the total CPU processing time required to arrive at the estimated total time for the scan.

Abstract: A data recording disk file includes a disk stack subassembly and a linear actuator, both of which are supported by a single-piece casting which forms part of the disk file housing. The casting is symmetric about two perpendicular planes and includes an open-ended portion and an actuator portion. The disk stack subassembly, which includes an in-hub motor, is entirely supported in the open-ended portion by two parallel interior walls which are equally spaced from the first plane of the casting. The linear actuator is entirely supported in the actuator portion by two parallel side walls which are equally spaced from the second plane of the casting. The actuator is mounted to the side walls in its plane of symmetry, which coincides with the first plane of the casting, and with its linear access axis coincident with the intersection of the two planes.