Abstract: A head assembly forming a field replaceable unit (FRU) is assembled and adjusted such that head-to-tape path alignments are accurately made completely independently of an associate tape drive device. The head assembly includes an aluminum base having a magnet and shield assembly attached to a back thereof. A head is attached to a rigid beam with a voice coil formed thereon and the head and beam are flexibly attached to the base with the voice coil functionally located for movement within the magnet assembly. A flag on the beam is sensed by an optical sensor attached to the base such that a horizontal position of the head can be sensed. An azimuth arm is attached to the front of the base having an azimuth and penetration datum affixed thereto. The azimuth arm is moved horizontally in relation to a mount plate of a data cartridge for azimuth adjustment. The penetration datum is adjusted for the penetration alignment relative to the mount plate.

Abstract: A high resolution, independent position sensor is provided, having application in a magnetic tape drive and other environments in which a linear or angular position is to be monitored. Analog outputs from an inexpensive, low resolution optical encoder are processed to correct gain and offset distortions and are used as the basis for an interpolation process. If a code strip having a 127-micron grating is used, a resolution of about 0.125 microns can be achieved.

Abstract: An improved and apparatus is provided in a tape drive for servo-controlling a tape head position relative to a magnetic tape as the magnetic tape travels past the tape head thereby reducing track mis-registration on the magnetic tape. Servo elements contained within the tape head detect a lateral displacement of the magnetic tape position relative to the tape head and generate position error signals corresponding to such lateral displacement. The position error signals are then filtered to generate a low frequency position error signal, a midrange frequency error signal, and position reliability signals. The tape head is then positioned by a head actuator according to the low frequency position error signal to adjust to the lateral movement of the magnetic tape. The midrange frequency error signal is compared to a distortion threshold to determine if errors exist due to tape edge vibrations or distortion of the magnetic tape.

Abstract: Diagnostic apparatus and method are disclosed for testing a Small Computer System Interface (SCSI), by passively monitoring the interface between initiator and target devices or systems, upon sensing a user-selected phase of operation at the interface, disconnecting the initiator and target devices from one another, forcing a user-selected fault for the appropriate time, and reverting to a passive monitor. A pair of analog switches are provided for each line of the interface. The switches selectively connect the initiator system and the target system to each other or to a set of line drivers for providing high or low SCSI signals. A set of sense lines are connected to the initiator and the target for monitoring so as to sense the phase of operation of the initiator and target and to sense the response of the interface to the forced fault.

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.

Abstract: When an automated data storage library includes the capability of storing and accessing more than one media type, it is necessary for the library manager to keep track of what media type is associated with each volume serial number ("VOLSER"), and where each is physically located in the library. For efficiency, VOLSERs will be grouped in sequential ranges, each range associated with a single media type (although a particular media type can be associated with different, non-contiguous ranges). When the number of VOLSERs and ranges is small, new ranges can be easily added, and existing ranges can be easily deleted or modified, manually by a system administrator. However, when the number of VOLSERs and ranges becomes large, it becomes burdensome for the administrator to track the VOLSER ranges and media types. An automated VOLSER range management system is provided which detects whether a new or modified range overlaps or is adjacent to an existing range with the same media type.

Abstract: A disk storage unit according to the present invention comprises a disk for storing data, a head for at least reading data stored on the disk, a controller for controlling a seek operation in which the head moves from a current track to a target track and a tracking operation in which the head tracks the target track after reaching the target track, based on a tracking error signal, and a device for adding a dc offset to the tracking error signal so that head drive power having a direction opposite that of the seek operation and corresponding to the velocity of the head in the seek operation is generated after the head has reached the target track and the seek operation has been switched to the tracking operation.

Abstract: A mailbox message system is coupled between a processor having a mailbox and one or more peripheral devices or circuits communicating information to the processor. The mailbox message system in the present invention reports events which occur in the peripheral devices or circuits to the mailbox within the processor to be serviced by the processor. The mailbox message system receives inputs from the processor indicating which events are allowed to be currently serviced by the processor and stores these inputs in a first memory. The mailbox message system further receives unique signals representing distinct events from the peripheral devices and stores these signals in a second memory. The generated events which are pending service in the second memory are then compared with the allowed events in the first memory. When a match exists, a message is encoded and transmitted to the mailbox of the processor indicating that the processor has an event to be serviced.

Abstract: A remote data shadowing system provides storage based, real time disaster recovery capability. Record updates at a primary site cause write I/O operations in a storage subsystem therein. The write I/O operations are time stamped and the time, sequence, and physical locations of the record updates are collected in a primary data mover. The primary data mover groups sets of the record updates and associated control information based upon a predetermined time interval, the primary data mover appending a prefix header to the record(updates thereby forming self describing record sets. The self describing record sets are transmitted to a remote secondary site wherein consistency groups are formed such that the record updates are ordered so that the record updates can be shadowed in an order consistent with the order the record updates cause write I/O operations at the primary site.

Abstract: The present invention provides an Input/Output station of an automated storage and retrieval system, or library, which uses an elevator mechanism to vertically translate a cartridge or a magazine containing a plurality of cartridges from a maximum vertical position above the top surface of the library to a minimum vertical position beneath the top surface and internal to the library. The Input/Output station is aligned with the other components of the library such that the vertical path of the elevator mechanism does not interfere with the path of the accessor. The operation of the Input/Output station does not pause the accessor and thus, does not interfere with the operation of the other automated processes within the library. Cartridges can be added to or removed from the library using the Input/Output station while the accessor is moving a different cartridge from a storage cell in the storage array to a drive.

Abstract: One or more stationary bar code readers are provided in an automated storage library to monitor the movement of magazines, cartridges and/or disks within the library and to maintain an updated inventory on the location of each item in the library. Preferably, a reader is positioned at the head of each column of storage cells and at the front of each drive unit. Each magazine and cartridge has a linear bar code label and each bare disk has a concentric bar code label. Each label is fixed to a surface visible to the readers whereby, as a magazine, cartridge or disk is passed in front of a reader, the label is read, decoded and the information used to update a library inventory table.

Abstract: A disaster recovery system providing asynchronous remote data shadowing between a primary and a secondary site uses a pair of track arrays for each primary data storage device of a remote copy pair to monitor which record updates are in transit between the primary site and the secondary site. A host processor at the primary site of the disaster recovery system transfers a sequentially consistent order of copies of record updates to the secondary site for back-up purposes. The copied record updates are stored on the secondary data storage devices which form remote copy pairs with the primary data storage devices at the primary site. One track array, the active track array, is used to set elements according to which tracks on the primary data storage device receive record updates from the host processor at the primary site.

Abstract: An apparatus and method are provided for amortizing the adverse performance impact of an erase-write-verify process for rewritable optical disks, with its numerous delays, over multiple sectors. A block of data to be written to a sector on a particular track of the disk is transferred from the host to a cache storage device. When a predetermined number of blocks to be written to the track have accumulated in the cache, destaging will occur. Those sectors to which the blocks will be written are erased in a single pass. Then the blocks are written to the erased sectors in the next pass. Verification of the written data, if desired, can be performed in a third pass. Consequently, only two passes per track (or three, if verification is desired) are required to record data from the host to the disk instead of two passes (or three) per block using conventional methods and the seek and latency delays are also reduced. Multiple tracks can be destaged in an order established by a controller.

Abstract: A head assembly forming a field replaceable unit (FRU) is assembled and adjusted such that head-to-tape path alignments are accurately made completely independently of an associate tape drive device. The head assembly includes an aluminum base having a magnet and shield assembly attached to a back thereof. A head os attached to a rigid beam with a voice coil formed thereon and the head and beam are flexibly attached to the base with the voice coil functionally located for movement within the magnet assembly. A flag on the beam is sensed by an optical sensor attached to the base such that a horizontal position of the head can be sensed. An azimuth arm is attached to the front of the base having an azimuth and penetration datum affixed thereto. The azimuth arm is moved horizontally in relation to a mount plate of a data cartridge for azimuth adjustment. The penetration datum is adjusted for the penetration alignment relative to the mount plate.

Abstract: A data storage system atomically suspends multiple duplex pairs across either a single storage subsystem or multiple storage subsystems. The duplex pairs are suspended such that the data on the secondary DASDs of the duplex pairs is maintained in a sequence consistent order. A host processor in the data storage system running an application generates records and record updates to be written to the primary DASDs of the duplex pairs. The storage controller directs copies of the records and record updates to the secondary DASDs of the duplex pairs. Sequence consistency is maintained on the secondary DASDs by quiescing the duplex pairs and then suspending the duplex pairs with change recording. Quiescing the duplex pairs allows any current write I/O in progress to complete to the primary DASD. The storage controller then locks out any subsequent write I/O from the host processor by raising a long busy signal to such subsequent write requests.

Abstract: A data storage system provides disaster recovery capability by asynchronously transmitting record updates to a secondary site in sequence consistent order. Such record updates are stored at a primary site in a cache memory of a storage controller. A circular queue is created having a head pointer for locating a first (or oldest) record update with subsequent record updates of a track being linked therefrom in sequence consistent order. A tail pointer of the circular queue points to the last record update. A counter field is provided in a track slot header for counting a number of updated records in the track and hence the circular queue. When a data mover in the host processor at the primary site reads record updates for transmission to the secondary site, the data mover starts with the record update pointed to by the head pointer such that the data mover moves through the circular queue (and hence the record updates) in a backward chain fashion.

Abstract: A remote copy system incorporates dynamically modifiable ports on the storage controllers such that those ports can operate either as a control unit link-level facility or as a channel link-level facility. When configured as a channel link-level facility, a primary storage controller can appear as a host processor to a secondary storage controller. The primary storage controller can thereafter initiate multiple request connects (RQC) concurrently for servicing a single I/O request. In this manner, a first available path can be selected and system throughput thus improved since RQCs so not need to be sent serially from path to path looking for an available path.

Abstract: The present invention provides a retainer system of an automated storage and retrieval system, or library, which prevents information storage elements, or cartridges, from escaping from their respective storage cells when the entire library is transported from one location to another. The retainer system comprises a retractable cable, a null, or dummy, cartridge, and an array of storage cells. One end of the retractable cable is attached to the null cartridge and the other end of the cable is affixed to one end of the array of storage cells. Initially, the null cartridge is positioned in a storage cell located adjacent to the end of the storage array where the cable is affixed. When all the information storage elements are placed inside their respective storage cells within the array, the null cartridge is moved from its original position to a storage cell at the opposite end of the storage array.

Abstract: A data processing system using a storage management server provides a method and apparatus for preserving consistency between a database back-up and a set of storage volumes. The system includes a plurality of client systems coupled to the storage management server. Primary and back-up copies of client files are stored within a set of attached storage volumes. The server contains a server database to maintain directory and reference location information linking the primary and back-up copies of the client files. The server periodically performs an incremental back-up of the server database to a database back-up. The server utilizes a reuse delay criterion to set selected storage volumes as pending volumes. Pending volumes are not eligible for reuse by the server, thereby preventing the server from overwriting these pending volumes and invalidating reference location information for the pending volumes stored in the database back-up.