Abstract: A data storage system includes a data storage medium, such as a magnetic tape, that has a first control data storing area or drive partition that is addressable only by a peripheral drive mounting the medium and a plurality of other addressable data storing partitions for storing data. A volume table of contents may be stored in one of the addressable partitions. A tachometer measures and indicates physical locations on the storage medium. Each of the partitions have an extent on the storage medium indicated by said physical locations. The control data in the drive partition includes directories of medium control blocks, such as tape marks, defect marks and the like; directory of all addressable partitions including the physical locations at the beginning of each partitions and other medium physical and logical parameter data. A so-called mount-demount medium control block in the drive partition indicates a demount status that shows all data stored in the drive partition is valid.

Abstract: A peripheral data storage subsystem has means for responding to a MOUNT command received from a host processor to create and mount a host-processor-addressable logical data-storage volume. Such logical data-storage volume has a serial number VOLSER indicated in the MOUNT command. The logical data volume is assigned a predetermined area of a physical data volume, such area being termed a partition. The illustrated embodiment shows a tape subsystem in which the partitions are accessed by a control using a reel tachometer that identifies segments of the tape. Each partition has a number of the tape segments. Controls and methods are described for initializing the subsystem for effecting the automatic volume creation, appending data into a logical volume, how logical volumes are made to be portable, moving logical volumes amongst diverse physical media, tape formats usable for such logical volumes, data base control of the logical volumes and volume creation processing.

Abstract: An automated tape library employing a motorized robotic picker wherein the electric motor driving the robotic picker is equipped with two brakes that act simultaneously. The first is a mechanical brake which uses a spring to push a brake pad against the rotating motor. During normal motor operation, an electric solenoid is used to overcome the spring and disengage the brake pad from the motor. When the robotic picker is to be mechanically stopped, the solenoid voltage is turned off and the solenoid releases the spring placing the brake pad in contact with the motor. The second brake is a dynamic electrical brake which makes use of the back emf of the motor to drive a current back into its own windings such that the motor decelerates.

Abstract: An automated storage library includes a robotic picker which moves linearly between linear and/or carousel storage shelves to transport data storage cassettes between the shelves and a data transfer device. The picker arm can swing in a vertical arc to access the tape stores on either side of its linear path. The arm also has at least one rotatable wrist and a pair of end effectors. A data storage cassette may be extracted from a data transfer device, the wrist rotated 180.degree., and a new cassette inserted. This reduces the number of times the robot has to visit the tape stores. The vertical arc movement of the picker arm provides for accurate orientation of the effectors with respect to the shelves and the data transfer devices.

Abstract: The utilization of a level of a data storage hierarchy is monitored and the data in such level is manipulated in response thereto. In a data storage hierarchy including an automated storage library, the utilization is a mount rate relative to the maximum possible mount rate. When the combined utilization of all of the libraries exceeds a predetermined value, data is promoted from the most utilized library (or libraries) to a higher level in the data storage hierarchy until the combined utilization of all of the libraries is sufficiently reduced. By reducing the combined utilization of all of the libraries, the average queue time for library mount requests is prevented from becoming excessively long relative to the average library mount cycle time.

Abstract: A tape drive subsystem discloses that variable length symbols can be used to reliably identify data stored on the tape. Machine controlling procedures are disclosed to encode and decode data for the reliable sensing of the serial number of a media, especially tape cartridges, having different track densities. The subsystem detects the serial number of the media and corrects, or at least detects, error patterns. A variable length symbol code is encoded in a plurality of groups with each group having a "one" being represented as an erase gap ERG signal covering a first two units of a group, and a "zero" is represented as one unit of an ERG signal, both followed by four units of an Inter Block Gap IBG signal.

Abstract: The invention is an automated storage library including one or more robotic accessors which move upon the surface of a horizontal plane including the openings to storage cells. The accessors are wireless, remotely controlled vehicles. The vehicles employ known tracking mechanism(s) to move between locations within the library. The storage cells are embedded beneath the horizontal surface. The horizontal plane is a floor which is formed by the surface of the storage cells. Openings in the floor are also the access openings to the storage cells. Storage media are raised and lowered into the storage cells by a picker mechanism on the vehicles.

Abstract: A magnetic tape drive simultaneously senses on a magnetic tape three evenly spaced-apart servo track areas for servoing a multi-track magnetic head to follow a concurrent set of data tracks on the magnetic tape. The data tracks are arranged into a plurality of track groups. Each track group has a first and second subgroup of data tracks. The first subgroup of tracks are scanned in a first relative motion of the magnetic tape and magnetic head as a forward direction (tape is being spooled from a supply tape reel). The second subgroup of tracks are scanned in a second relative motion of the magnetic tape and magnetic head that is opposite in direction to the first relative direction and is a forward direction of scanning. While writing data in any one of the plural track groups, a servo dropout affecting most of the servo track areas is detected and indicated as a servo error. Writing is aborted. The relative position of the magnetic tape and head is detected at both longitudinal ends of the servo dropout.

Abstract: An automated tape library employing a motorized robotic picker wherein the electric motor driving the robotic picker is equipped with two brakes that act simultaneously. The first is a mechanical brake which uses a spring to push a brake pad against the rotating motor. During normal motor operation, an electric solenoid is used to overcome the spring and disengage the brake pad from the motor. When the robotic picker is to be mechanically stopped, the solenoid voltage is turned off and the solenoid releases the spring placing the brake pad in contact with the motor. The second brake is a dynamic electrical brake which makes use of the back emf of the motor to drive a current back into its own windings such that the motor decelerates.

Abstract: An automated storage library for which the management thereof is transparent to a requester is disclosed. The library provides for all of its own internal management. To access a file in the library, a requester need only specify the volume on which the file is located, permitting the use of a standard file access method for a single peripheral storage device. A path format which is the same as that used for a single, peripheral storage device, except that the peripheral storage device designator is replaced with a designator for the automated storage library and a volume label is inserted as a subdirectory path element, and a program product therefor are also disclosed.

Abstract: A method for servicing a mount request in an automated storage library in which all of the peripheral storage devices therein are occupied and which permits an active data storage medium to be temporarily demounted and subsequently remounted in any subsequently available peripheral storage device is disclosed. To service a mount request requiring that a data storage medium be demounted, the access information for the data storage medium to be demounted is first retained. After demounting and servicing of the mount request, the retained access information is used to permit remounting of the previously mounted data storage medium in any subsequently available peripheral storage device, thereby minimizing the risk of delay in remounting. The method also allows for optional parameters to prevent temporary demounting in an automated storage library, or to prevent temporary demounting of particular data storage media. An automated storage library and program product employing the method are also disclosed.

Abstract: An optical disk having its disk inventory at the picker level is disclosed. The library includes two library controllers and four pickers. Each library controller maintains a list of the storage media in the entire library, but has no disk location inventory. The library controllers are not coupled to each other. Each picker has exclusive access to a set of storage cells and internal peripheral storage devices. In addition, the picker controller for each picker maintains the disk location inventory for the disks accessible by such picker. During a failure condition which prevents one library controller from accessing a particular storage medium, the other library controller can be signalled to attempt to access such storage medium. The overhead associated with maintaining two identical copies of the inventory in the library controllers is therefore eliminated.

Abstract: A robotic manipulator for picking and placing data storage cassettes in an automated storage library. The manipulator has a pair of fingers, one finger being longer than the other. An eject bar is located between the fingers and has a tab for pushing a storage cassette into the seated operative position in an IBM 3480 type tape reader. The manipulator approaches the slot in the reader, supporting the data cassette on the long finger and holding it in place with the short finger. The short finger pivots to free the cassette and the eject bar pushes it into the reader. When the eject bar is clear of the long finger it pivots downwards so that the tab engages the top of the cassette and pushes it into the seated position in the reader.

Abstract: A robotic system has a transfer bay through which objects may be exchanged with a robot. An internal door allows the robot to access the transfer bay and an external door allows access to the transfer bay from the exterior. The external door can only be opened when the internal door is closed and when the robot is denied access to the transfer bay. This means that personnel inputting or outputting objects to the robotic system cannot come into contact with the robot. When the robotic system is an automated storage library the transfer bay may comprise any number of available storage shelf bays and thus the size of the transfer bay may be varied.

Abstract: A method and apparatus which first calculates track to track skew in a tape device and then uses the results of that calculation to adjust the windows for detection of sync and resync characters. The system makes use of global circuitry which adjusts the sync and resync windows for all tracks based upon the skew calculation. In the case of the windows used for detecting resyncs, when skew is determined to be large, the global resync window must span a larger time period to account for the skew in detecting resync marks. Conversely, when there is little or no skew present, the windows for resync detection can be narrowed. Normally, the track logic utilizes its own local windows to detect resyncs. If a track misses a resync, however, it must use the global resync window to determined the next resync location. Once the tracks are resynchronized, control can return to local track circuitry to maintain synchronization.

Abstract: An automated tape library employing a motorized robotic picker wherein the electric motor driving the robotic picker is equipped with two brakes that act simultaneously. The first is a mechanical brake which uses a spring to push a fixed brake pad against the rotating motor. During normal motor operation, an electric solenoid is used to overcome the spring and disengage the brake pad from the motor. When the robotic picker is to be mechanically stopped, the solenoid voltage is turned off and the solenoid releases the spring placing the brake pad in contact with the motor. The second brake is a dynamic electrical brake which makes use of the back emf of the motor to drive a current back into its own windings such that the motor decelerates. The circuit further prevents mechanical brake engagement even at lower motor speeds when back emf is relatively low but robot speed is fast enough to cause mechanical damage if stopped via the mechanical brake.

Abstract: The response time of an automated optical disk library is improved by writing object delete requests to a deleted objects table before actually physically deleting those objects. By collecting object delete requests in a list of pending deletes for each volume in the library the number of necessary mounts are reduced. The delete requests in a list of pending deletes for a given volume are physically deleted just prior to performing a write or defrag request for that volume. The list of pending deletes for that volume are then deleted from the deleted objects table. During idle periods a predetermined number of pending delete requests will be performed for the currently mounted volume. If there are no pending delete requests for the currently mounted volume then a predetermined number of pending delete requests will be performed on the opposite side of the currently mounted volume.

Abstract: To accomplish both fast track access and low power consumption in an apparatus for recording or reading out a signal onto or from a track of a recording medium. The actuator control apparatus uses a tracking error signal (TES), which is a signal whose level varies, with the time taken for a pickup to cross one track being used as a cycle. It detects the velocity of the pickup from the time interval (Ti) of the mean level crossing by TES, and provides an actuator with a signal having a pulse width (Tf) proportional to the time interval of the mean level crossing by TES, in synchronization with the crossing of the mean level by TES.

Abstract: Two identical CRC circuits are cross coupled to make alternate CRC calculations based on the other CRC circuit's calculation. Throughput of the CRC code calculation is improved by applying alternate input data simultaneously at each of the CRC circuits so that when one calculation is completed the next input data is available to immediately begin the next calculation. The output of each CRC circuit is fed into one of two latches that make up an LSSD register such that the first latch captures the first CRC calculation on a first clock of non-overlapping clocks. The second CRC calculation is captured by the second latch on a second clock of the non-overlapping clocks. Two CRC calculations can be made in one period of the non-overlapping clocks while avoiding race problems.