Abstract: A method for producing a magnetic structure, such as a thin film magnetic head, in which the magnetic and electrical characteristics of magnetic material are tailored to produce magnetic and electrical characteristics in selected localized areas of the magnetic material. In a specific embodiment, the structure comprises a layer of magnetic material having an overlayer and an underlayer, and the magnetic characteristics of the material are modified by rapid thermal annealing.

Abstract: According to the present grinding method, a plurality of optical markers are formed by photolithography such that the markers are embedded in a chiplet having a magnetic head. Markers are preferably in the shape of a bar having predetermined height, width and length and are spaced from each other by a predetermined distance where one end of the bars are sequentially offset from each other by a predetermined amount. During coarse grinding of the magnetic head as the magnetic head surface material is ground away, the end-face of the bars, one at a time, become visible. The closer the grinding surface approaches the desired inductive throat or MR element height, more end-faces become visible. Coarse grinding continues until a predetermined number of end-faces become visible at which point the grinding process is terminated and the magnetic head is ready for the final lapping process.

Abstract: In a client/server environment, a method and means for reducing the storage requirement in the backup subsystem and further reducing the load on the transmission bandwidth where base files are maintained on the server in a segmented compressed format. When a file is modified on the client, the file is transmitted to the server and compared with the segmented compressed base version of the file utilizing a differencing function but without decompressing the entire base file. A delta file which is the difference between the compressed base file and the modified version of the file is created and stored on a storage medium which is part of the backup subsystem. Alternatively, a copy of frequently accessed base files are maintained on the client in a compressed format. Whenever the client detects that a frequently accessed file has been modified, the modified version of the file is differenced against the base version of that file without decompressing the entire base file and a delta file is generated.

Abstract: A housing designed to accommodate a plurality of removable electrical devices includes power connectors mounted within the housing for connecting a power source to each of the devices. In order to prevent a user from inadvertently contacting live connectors within the housing, the housing is provided with one or more safety elements e.g., in the form of fins fixed in the cavity which are positioned to lie between adjacent devices. The position, size and location of the pins are strategically chosen to prevent access to the connector(s). The position of the fins between the devices allows the user access to the devices to load and unload them into and from the housing.

Abstract: The invention is a write clock generator circuit adapted for use in disk drives having either dedicated servo or sector servo architecture. A high frequency write clock signal is generated from a relatively low frequency reference signal synchronized to disk rotation. The reference signal may originate from a number of sources, including a dedicated servo pattern, a sector servo pattern, any index pattern, or a spindle pulse. A clock generates a clock signal having a predetermined number of cycles for each reference period. A counter coupled to the output of the clock counts the number of clock cycles generated for each reference period. The number of cycles is then compared to an expected number corresponding to a desired clock frequency. If the compared numbers are not the same, an error signal is generated. Control logic receives the error signal and the reference signal, and generates an appropriate control signal.

Abstract: This invention provides a method and apparatus for accurately measuring the flying height of a magnetic head at high speed by using a white lamp and a color CCD camera. The invention entails substituting tentative refraction coefficients and extinction coefficients representative of colors in theoretical equations expressing the relationship between interference light intensity and flying height, thereby optimizing the parameters by non-linear regression. The flying height of a magnetic head is measured by using the coefficient thus determined. Also, this invention enables determination of flying height at very high speed through effecting the above optimization in consideration of constants associated with the shape of the head under consideration, and adapting the above theoretical equations.

Abstract: A micropolarimeter comprises an analyzer (1) and a detector (3), which is typically a photodetector array. The detector has a circular configuration of a number N of sectors. Analyzer (1) and detector (3) form a unit with the analyzer assigning different polarization values to the sectors. Analyzer and the detector contain no moving parts. Three different embodiments are proposed for the analyzer: a glass cone, covered with a polarizing thin film stack, a metal grid polarizing array, and an array of polarizing waveguides. The micropolarimeter (14) is used preferably in a microellipsometer system which can serve as a tool for film diagnostics, especially optical characterization of thin films.

Abstract: Dynamic allocation of read cache space is allocated among bands of DASD cylinders rather than to data sets or processes as a function of a weighted average hit ratio to the counterpart cache space. Upon the hit ratio falling below a predetermined threshold, the bands are disabled for a defined interval as measured by cache accesses and then rebound to cache space again.

Abstract: The improved disk drive system has an improved actuator arm assembly where the arms are independently and individually insertable and removable from the actuator member. Furthermore, each arm is individually self-locked into the actuator member without the need for external retaining means such as screws, springs, and rings. Since the arms are individually insertable/removable, the arms can be made very thin thereby allowing easy attachment of the head suspension assembly to the arm without the need for swaging, bonding, welding or screw-in. Since the arms can be made very thin, that provides substantial reduction in disk to disk spacing and therefore, substantial reduction in the overall height of a disk drive system.

Abstract: A computer implemented method for speeding up the recursive most significant digit radix sorting of a set of record keys in which the keys are scanned for a shared or common prefix, coded according to the point in the key where they differ and the value of the differing digit, and processed such that during each dispersion phase the code words are used to speed processing by avoiding comparison matching of the prefixes, the recursive dispersion and collection phases continuing until singletons are reached. In the absence of shared prefixes the keys are normally recursively radix sorted.

Abstract: This high-density optical data storage unit comprises a storage medium supported on a mechanically stable substrate, and a read/write arrangement employing a plurality of laser light sources and an interrogation light source. The laser light sources are designed as laser diodes attached to a substrate and optically aligned with an equal plurality of microlenses integrated in a first transparent layer. The read/write arrangement further comprises at least one second transparent layer, and an optional semitransparent conductive coating, said layer or said coating carrying a plurality of particulate protrusions which are also aligned with said diodes and said microlenses, said storage medium and said read/write arrangement being maintained in a mutually parallel alignment with a gap in between having a width of less than 100 nm. The protrusions in combination with the laser light sources produce dints in the medium which are representative of the data to be stored.

Abstract: A method and means for achieving files of modifiable pages in a log based phased commit transaction management system (TMS) in which those pages which have been modified since the last full or incremental backup donot require during the copy operation any modifications to the page itself but merely to a common status page. This is accomplished by management of a pair of global log sequence numbers. Comparison between a first number (ICBU.sub.-- LSN) and each data page LSN as the page is modified permits the common status page to be updated to correctly reflect the changed status. Subsequent modifications to the same page donot require amendment of the status page. The status page indicia are reset as part of the backup procedure and for ascertaining the page copy set for incremental copying. The ICBU LSN assumes one of two values as a function of the copy operation and another value for processing page modifications after the copy operation. A second number (ICRF.sub.

Abstract: A method and means is disclosed for dynamically partitioning an LRU cache partitioned into a global cache storing referenced objects of k different data types and k local caches storing objects of a single type. Referenced objects are stored in the MRU position of the global cache and overflow is managed by destaging the LRU object from the global to the local cache having the same data type. Dynamic partitioning is accomplished by recursively creating and maintaining from a trace of objects an LRU list of referenced objects and associated data structures for each subcache, creating and maintaining a multi-planar array of partition distribution data from the lists and the trace as a collection of all possible of maximum and minimum subcache sizing, optimally resizing the subcache partitions by applying a dynamic programming heuristic to the multiplanar array, and readjusting the partitions accordingly.

Abstract: An optical data storage device having a substrate has guide ridges, or reverse grooves, in a concentric or spiral shape formed thereon, and disposed in a plane parallel to and disposed from the substrate surface. The device further has pits formed approximately midway between the guide ridges and disposed in the substrate and having bottoms below the plane of the substrate surface. A method for manufacturing the optical data storage device having both address pits and guide ridges is disclosed. A dual tone photosensitive material is applied to a substrate, exposed with a laser light source comprising two distinct wavelengths, and developed to provide a desired bipolar geometry thereon.

Abstract: A Viterbi decoder having a recursive processor modified to process each node in a trellis of a partial response coded signal to shift the branch metric additions over the node to effectuate compare, select, add operation order on the predecessor survivor metrics terminating in that node, to compare the metrics of the predecessor sequences terminating in the node, to select a survivor sequence, and to add the shifted branch metrics to the metric of the selected survivor sequence.

Abstract: The present invention is a controller and a method for its use in a disk data storage and retrieval system. The controller is of the type which associates a file mask with a sequence of commands. The controller has means for executing a critical-section-start (CSS) command received from the host computer which indicates to the controller that a critical sequence of commands will follow and places the controller in a critical sequence mode (CS mode). The controller has means for executing a critical-section-end (CSE) command which indicates the end of the commands. While in the CS mode the controller checks the file mask for each command received and refuses to execute selected commands which are not associated with predetermined values of the file mask (CS file masks). A program running on the host computer sends the controller a command establishing a CS file mask and the CSS command, then the program sends one or more sequences of critical commands to the controller.

Abstract: A data storage and retrieval system is provided which has extremely high capacity. The system includes a large array of small disk files, and three storage managers for controlling the allocation of data to the array, access to data, and the power status of disk files within the array. The allocation manager chooses the disk files upon which incoming data is written based on the current state of the disk files (active or inactive), the available capacity, and the type of protection desired (i.e unprotected, RAID), mirrored, etc.). The access manager interprets incoming read requests to determine the location of the stored data. The power manager sequences disk files between active and inactive to provide the storage requested by the access and allocation managers.