Abstract: Disclosed is an invertible portable tape container for containing two separate lengths of recording tape for providing rapid access to data. The container may be inserted into a tape drive, preferably by an automated data storage library robot, in either of two relatively inverted positions, allowing rapid access to either of the two separate lengths of recording tape. A generally rectangular housing includes two access openings, respectively to the right side and to the left side. Four tape spools are positioned within the housing, with the spools at one side inverted with respect to those on the other side. Separate sets of tape bearings each supports one of the lengths of recording tape at one of the access openings.

Abstract: Disclosed are robust Resync patterns for insertion into a run length limited (d,k) encoded channel bit stream, which Resync pattern may be recovered from the RLL (d,k) encoded bit stream without being confused with data. The Resync pattern includes at least one string of consecutive "0"s which exceeds the RLL (k) constraint, and is inserted into the channel bit stream RLL data codewords. The RLL code excludes certain patterns representing a bit shift from the Resync pattern of one or both "1" bits adjacent to the string of "0" bits, shifted to shorten the Resync pattern to within the (k) constraint. Additionally, the Resync pattern may have two different aspects, one of which is the string of "0"s violating the constraints of the RLL code, and another which is specifically excluded from the RLL code, such as an excluded concatenated sequence of a VFO bit pattern of predetermined length or greater.

Abstract: An input/output (I/O) data compression system operates two data compression modules in tandem. A "master" module has an uncompressed data I/O, a data compressor/decompressor, a data flow manager, and a compressed data I/O. An identical "dual" data compression module is also provided. Either module is capable of operating singly to provide compression/decompression between the data I/Os. A "tandem" control causes the master data flow manager to control the compressed data I/O, and causes the dual data flow manager to relinquish control. A dual port "active/slave" control responds to receipt of an input at one of the uncompressed data I/O's, idling the uncompressed data I/O of the module (slave) not receiving the input, and causing the module (active) receiving the input to conduct the input and output of uncompressed data.

Abstract: Disclosed is an automated data storage library in which a library accessor, arranged for accessing data recording media stored in storage bins, may also exchange electronic components of the library. The media are provided with access engagement surfaces for engagement by the library accessor(s). A plurality of removable mounts, having access engagement surfaces matching the data recording media access engagement surfaces, are provided for individually mounting electronic components, such as data storage drives and communication jumpers. Component slots are provided in the library for individually supporting the removable mounts, and mating low insertion force connectors are provided respectively on the removable mounts and ones of the component slots for removably connecting the electronic components to the library.

Abstract: A rewind tape drive is disclosed for a tape library for rewinding a tape upon a read/write tape drive of the library completing reading and/or writing a tape. In some instances, the tape may be positioned close to the beginning of tape at the completion of reading and/or writing. Thus, the disclosed invention may additionally, upon completion of reading and/or writing a tape, determine whether the time required for the tape drive to rewind the tape exceeds a predetermined time, and transport the tape to the rewind unit only upon exceeding the predetermined time. The predetermined time may comprise the time required for unloading the tape from the read/write tape drive to an accessor, the time required for the accessor to transport the tape to the rewind unit, and the time required to load the transported tape into the rewind unit.

Abstract: Disclosed are an automated data storage library having a plurality of pickers with multiple grippers and a method for operating the library to respond to received input commands which require an exchange of media at a point of exchange (e.g., at a storage slot or read/write station), by first determining whether the source and destination locations for the media to be exchanged are on opposite sides of the point of exchange. Next, if the source and destination locations for the media to be exchanged are on opposite sides of the point of exchange, the exchange is decomposed into separate moves, and each of the separate moves is assigned to a different one of the pickers.

Abstract: A data storage system provides a method and apparatus for preserving consistency between a database back-up and a set of storage volumes. The system includes a storage manager, or storage controller, interconnected to a plurality of storage volumes, a drive, and a database storage. The storage manager receives data files from an attached data processing unit. The storage manager directs the data files such that the files are written to a selected storage volume loaded into the drive. The storage manager maintains reference information and storage volume location information for each data file in the database storage. The storage manager detects a volume full condition when the storage media approaches a predetermined position prior to the physical end of the volume. The storage manager generates a back-up copy of the current database, transfers the database back-up to the drive, and directs the drive to write the database back-up onto the selected storage volume.

Abstract: This invention permits users to conveniently examine functions, applications, data, and other parameters for different periods of time. A region of the graphical user interface is provided to which other icons may be dragged so that the function represented by the dragged icon returns to a prior state or is extrapolated to a future state. By storing the previous m versions of a file, application, database, etc., where m is user selectable, the user can review prior versions of that file, application, or database without explicitly having to track those versions. The graphical nature of the present invention provides a significantly more intuitive way to manipulate the time.

Abstract: A unique and permanent identifier is provided for removable media. The identifier is preferably recorded in a previously unused or reserved portion of the media and can be generated from a combination of the originating drive serial number and the current date and time with a random number concatenated thereto. When a piece of media is loaded into a drive, the drive examines the reserved area for the presence of an identifier. If not present, the drive generates and records an identifier before performing whatever disk access operations have been requested. If the identifier is present, the drive is prevented from overwriting the identifier with a new one and the disk access operations are performed immediately. Once the media is provided with its identifier, the media, and any errors associated with the media, can be tracked throughout its life.

Abstract: A storage and retrieval library has a column of storage cells including at least some side-by-side storage cells. A media accessor with a picker gripper for accessing media in one side of the side-by-side cells is rotatable about a pivot to an opposed position for accessing media in the other side of the side-by-side cells. For multi-sized media, a column may have storage cells extending the full width of the column for holding a large sized media, and a second type of smaller cells arranged side-by-side, each for holding a small sized media. A media picker has a first gripper for accessing large sized media from the full width cells, and a second gripper for accessing small sized media from one side of the side-by-side cells. The media picker is rotatable about a pivot to an opposed position for the second gripper for accessing small sized media from the other side of the side-by-side cells.

Abstract: Disclosed is a magnetic tape media having addressing data information superimposed on prerecorded track following servo information. The servo information is recorded in magnetic flux transition patterns defining at least one longitudinal servo track. A servo burst pattern of at least two repeated pairs of non-parallel magnetic flux transitions is provided, at least one of which transitions is slanted or otherwise continuously longitudinally variable across the width of the servo track. At least two transitions of the repeated pairs are shifted longitudinally with respect to other of the transitions, the shifted transitions comprising the superimposed addressing data information.

Abstract: A data transfer system providing parity uses a method and apparatus for transmitting a data clocking signal in a parity bit location along a data bus to latch an accompanying data byte at a receiving device. A transmitting device, coupled to the receiving device through the data bus, generates a data clock signal and latches the clock signal into the parity bit location of the data bus. The clock signal and data byte are then transmitted along the data bus to the receiving device. The receiving device uses the clock signal to latch the data byte from the data bus. Thus, the data transfer system uses the data clock signal transmitted in the parity bit location of the data bus to validate and synchronize the accompanying data byte at the receiving device.

Abstract: A virtual data storage system provides a method and apparatus for adaptively throttling transfers into a cache storage to prevent an overrun in the cache storage. The virtual data storage system includes a storage interface appearing as a set of addressable, virtual storage devices, a cache storage for initially storing host-originated data files, storage devices for eventually storing the data files on a set of storage volumes, and a storage manager for directing the data files between the cache storage and the storage devices. An amount of available space in the cache storage, or a cache free space, is monitored against an adjustable cache space threshold. A storage throttle is computed when the cache free space drops below the cache space threshold. Additionally, a recall throttle is computed based on the cache free space and a number of storage devices reserved for recalling data files from the set of storage volumes.

Abstract: Disclosed is a coding technique which takes advantage of the use of an internal synchronization technique for a timing-based servo which employs alternating 4 and 5 transition bursts of servo to provide a simplified synchronization of the data, and comprises a coding technique which employs a periodic pattern of bursts each period comprising two bursts of 5 transitions followed by two bursts of 4 transitions. The code provides, in each burst of 5 transitions, two defined positions for the 2nd and 4th transitions, spaced from equally spaced positions in the burst, to represent each of two bit values. The code provides, in each burst of 4 transitions, two defined positions for the 2nd and 3rd transitions, spaced from equally spaced positions in the burst, to represent each of two bit values.

Abstract: A method for establishing bilateral communications over a single ESCON link coupling a pair of control units. The method steps include (a) permitting link address acquisition between directly connected link-level facilities that simultaneously assume the role of a master control unit in a peer-to-peer remote copy (PPRC) configuration, (b) resolving conflicting device-level frames that initiate a path to a device (also termed an I/O connection), and (c) dynamically determining the role assumed by a link-level facility (master or slave) when a single logical path is shared.

Abstract: Disclosed are a programmable digital device and method for generating tracking threshold signals for qualification of input peak signals in response to programmed digital gain signals which control the rate at which the envelope of the qualified input peak signals is followed, and in response to a programmed digital attenuation signal which determines the proportion of the peak envelope at which to generate new tracking threshold signals. The programmable digital device and method also provide a programmed clamp signal to clamp the positive and negative threshold signals to not fall below the programmed values. An anti-hang capability is provided to allow the thresholds to drop after a programmed time period during which no signal is detected. In an alternative arrangement, the centerline of the envelope is followed and used as the threshold.

Abstract: A memory controller design includes at least one memory instruction decoder de-embedded from a memory instruction processor wherein the memory instruction processor receives operations and logical address information from a host processor. The memory instruction processor converts the operations into generic memory instructions and translates the logical addresses into physical addresses. The memory instruction decoder further converts the generic memory instructions into memory specific control signals and converts the physical addresses into actual memory specific addresses. This design permits the memory instruction processor to be designed and finalized before an actual memory type is selected for system use at which time the less complex memory instruction decoder can be designed.

Abstract: An automated data storage library is disclosed for quickly switching to a second accessor when a first accessor fails. Either the first or the second accessor may be designated an active accessor and the other a standby accessor. The library includes first and second library managers, one designated an active library manager and the other a standby library manager, each of the library managers interconnected with one of the accessors for operating the interconnected accessor, and each interconnected with the other of the accessors for operating the interconnected other accessor. The active library manager may operate the first accessor as an active accessor and, upon the first accessor becoming unavailable, immediately switches to operate the second accessor as the active accessor and allows maintenance and servicing of the first accessor simultaneously with operation of the second accessor.

Abstract: Disclosed is a portable tape cartridge for containing two separate lengths of recording tape for providing rapid access to data by a single tape drive. Two access openings on the inboard side (with respect to the tape drive) of the tape cartridge are respectively positioned toward the left or right. Two sets of tape bearings each respectively supports a length of tape at each of the access openings, and each length of tape is wound on two tape spools. The left set of tape bearings and tape spools are positioned with respect to each other identically to the positioning of the right set of tape bearings and tape spools with respect to each other. This allows the cartridge to be translated sidewise by the tape drive for reading and writing on the left or the right length of tape.

Abstract: A magnetooptical disk recording device has a far-field detector for detecting radial position of a laser beam with respect to tracks on the disk. The far-field detector has a reference line dividing first and second photo detectors. The reference line is centered radially with respect to center lines of the tracks. The reference line is also center lengthwise to be tangentially center with respect to a tangential point on the track. The detector is adjustable both radially and tangentially. The tangential adjustment is based upon sensing two low reflective calibration marks on the disk that indicate centering the laser beam, hence the track tangent point, on the reference line. The calibration is based upon obtaining minimum noise in the detector output signal that signifies that the laser beam is centered on the length of the detector reference line. The calibration marks are in a mirror area disposed at one radial extremity of the disk.