Hitachi, Ltd.

Minoru Kosuge

Terumi Takashi

Kazunori Iwabuchi

Kenji Yamagami

Hiromi Matsushige

Hideki Miyasaka

Hiroshi Arakawa

Koichi Kimura

Takashi Oeda

Takashi Kobayashi

Shigemitsu Higuchi

Haruaki Watanabe

Kouji Fujita

Atsuo Suga

Takashi Doi

Kenzo Kurihara

Toshiro Aizawa

Kenzo Tabata

Naoto Matsunami

Manabu Kitamura

Naoki Watanabe

Yoshihisa Kamo

Hiroyuki Kitajima

Shinichi Arai

Kazuaki Tanaka

Akihiko Hirano

Yoshihiro Uchiyama

Yasuhiro Katoh

Tsuguji Tachiuchi

Naoki Sato

Michio Miyazaki

Norihisa Komoda

Isao Tsushima

Yoshiteru Ishida

Hideyuki Yamakawa

Toshifumi Nishimura

Tatsuo Namba

Katsuharu Kakuse

Kenichi Kageura

Satoshi Minoshima

Sadasaburoh Kanai

Masaru Teranishi

Ai Tanaka

Yasuhiro Shimura

Soichi Oyama

A data sharing method for use in a computer system provided with a first computer, a second computer and a data storage subsystem for connection with the first and second computers is disclosed. The data storage subsystem has a plurality of memory units and a control unit for controlling the plurality of memory units. The control unit forms a paired state of a first memory unit storing data for use by the first computer and a second memory unit, the paired state being so controlled as to match the contents of the first memory unit and those of the second memory unit. When data used by the first computer are to be used by the second computer, the control unit releases the paired state between the first memory unit and the second memory unit to stop updating of the first memory unit to be reflected in the second memory unit. After that, the control unit re-maps a third memory unit used by the second computer and the second memory unit with each other, and so performs control that the access by the second computer to the third memory unit be made to the second memory unit.

Computer system and data sharing method between computers

In a computer system having a computer, a storage system having storage units being coupled to the computer and for storing user data used by the computer, and a backup device being coupled to the computer and the storage system, a backup method is presented for obtaining a backup of the data stored in the storage unit to the backup device. The storage system holds the user data dually in a first and a second storage units. In backing up the user data, a split instruction for releasing the duplex state of the first and the second storage units is sent from the computer to the storage unit. In response to the split instruction, the storage system interrupts the reflection of the update of the user data to the first storage unit onto the second storage unit. Then, a copy instruction for copying the user data held in the second storage unit to the backup device is sent from the computer to the storage system. The storage system operates to transfer the user data inside of the second storage unit to the backup device in response to the copy instruction.

Method of data backup in a computer system and a storage system therefor

Count pulses CTP from a counter 15 are supplied to a phase detector 3 through a two-frequency-divider 17 to produce measurement data N.sub.1 representing a difference in phase from a synchronized peak pulses PK. In a subtractor 4, the measurement data N.sub.1 is compensated with error data Ne from a register 13 in order to reduce the number of steady-state phase errors. An internal phase error .DELTA.N produced by the subtractor 4 is supplied to an LPF 5, undergoing compensation processing in a digital filter 7 thereof. The LPF 5 also includes a phase compensator 6 and a period compensator for compensating a control delay experience by the internal phase error .DELTA.N in the digital filter 7. An integer part OPD1 of counter oscillation period data OPD output by the LPF 5 is used for determining an oscillation period of a counter 15 whereas a fraction part OPD2 thereof is accumulated in a register 12 through an adder 11. An error accumulated in a register 12 is transferred to a register 13 and stored therein as error data Ne. Accordingly, the acquisition time is shortened and the number of steady-state errors is also reduced as well.

Digital phase-locked loop circuit

Count pulses CTP from a counter 15 are supplied to a phase detector 3 through a two-frequency-divider 17 to produce measurement data N.sub.1 representing a difference in phase from a synchronized peak pulses PK. In a subtractor 4, the measurement data N.sub.1 is compensated with error data Ne from a register 13 in order to reduce the number of steady-state phase errors. An internal phase error .DELTA.N produced by the subtractor 4 is supplied to an LPF 5, undergoing compensation processing in a digital filter 7 thereof. The LPF 5 also includes a phase compensator 6 and a period compensator 8 for compensating a control delay experience by the internal phase error .DELTA.N in the digital filter 7. An integer part OPD1 of counter oscillation period data OPD output by the LPF 5 is used for determining an oscillation period of a counter 15 whereas a fraction part OPD2 thereof is accumulated in a register 12 through an adder 11. An error accumulated in a register 12 is transferred to a register 13 and stored therein as error data Ne. Accordingly, the acquisition time is shortened and the number of steady-state errors is also reduced as well.

Digital phase-looked loop circuit

A magnetic tape drive in a helical scan system can shorten retry operation time. A data signal reproduced from magnetic tape through reproducing heads is supplied to a regenerative signal processing circuit. If an uncorrectable error is contained in the signal, the regenerative signal processing circuit outputs error information to a system controller. Then, the system controller sends a retry instruction to a movable head controller. When receiving the retry instruction, the movable head controller supplies movable head control signals to displacement elements which then displace the reproducing heads along a rotating shaft of a rotary drum for re-scanning an error occurrence data track. This retry operation is repeated until no error is detected. The magnetic tape is run at lower speed or is stopped as required during the repetitive retry operation.

Magnetic tape drive with displaceable head capable of a re-try operation

In an automatic library system for transportable data storage units, a library storage control reduces the chances of contention for file mounting. The magnetic tape library system 3 includes first read/write apparatus 20 with automatic mounting and second read/write apparatus 30 not requiring automatic mounting. Depending on the utilization of the first read/write apparatus 20, write data is recorded temporarily in a common storage installed in the second read/write apparatus 30. When the utilization of the first read/write apparatus 20 is low, the temporarily stored data is automatically transferred to a data storage unit in the first read/write apparatus 20 in which the data should normally be stored. The handlers and the first read/write apparatus 20 can be used with priority for handling data storage units for read data that require transport from the storage shelf or holder. The apparent number of the read/write apparatus increases by an amount equal to the number of data writes, improving the system throughput.

Magnetic tape library system wherein write request to a storage unit to

A data recording and reproducing apparatus of a helical scanning system includes a unit for recording and reproducing an information signal in an oblique information track on a magnetic tape by a rotary magnetic head and a unit for recording and reproducing a control signal on the magnetic tape in a longitudinal direction thereof. Further, the data recording and reproducing apparatus includes a memory unit for storing a difference (X-value error information) between a predetermined X value and a distance (X value) between a record starting position of the information track and a recorded position of the control signal, a unit for recording X-value error information on the magnetic tape individually each time information is recorded, a unit for reproducing X-value error information on the magnetic tape, and a unit for shifting a reproduced phase of the control signal in accordance with the X-value error information.

Data recording and reproducing apparatus

An AGC circuit is provided with a variable gain amplifier which changes an amplification gain of an input signal in accordance with an instruction; an extraction unit for extracting a value of an output of the variable gain amplifier at a predetermined interval; and a variable gain control unit for instructing the amplification gain of the variable gain amplifier in a manner such that the amplitude of the input signal is equal to a predetermined amplitude on the basis of the value extracted by the extraction unit. The variable gain control unit is provided with an error signal output device for squaring the value extracted by the extraction unit and for generating an error signal to instruct the amplification gain of the variable gain amplifier in a manner such that the amplitude of the input signal is equal to a predetermined amplitude on the basis of the square value and a square value just before it; and an integrating device for integrating the error signal from the error signal output device and for instructing the amplification gain of the variable gain amplifier.

AGC circuit and recording and reproducing apparatus using AGC circuit

A data reproducing circuit having a magnetic head for reading data from a recording medium, an adaptive equalization circuit for optimizing the waveform of a read signal, a discriminator circuit for discriminating an output signal of the adaptive equalization circuit and outputting a discriminated signal to an upper stage circuit, a format detecting circuit for detecting a pattern of signals written on the recording medium from outputs of the magnetic head, an expected value generating circuit for generating an expected value of the waveform of the read signal in accordance with an output of the adaptive equalization circuit and an output of the discriminator circuit, and an error detecting circuit for generating an error signal representing a difference between an output of the adaptive equalization circuit and an output of the expected value generating circuit. In the data reproducing circuit, the adaptive equalization characteristic of the adaptive equalization circuit is changed when a particular signal pattern on the recording medium is detected, allowing the adaptive equalization operation suitable for the recording medium.

Adaptive equalization circuit for magnetic recording apparatus having

A magnetic tape data management method and apparatus is described that reduces the access time for updating and referring to directory data. At the time of accessing data on a magnetic tape loaded in a magnetic tape subsystem, directory data for the magnetic tape is, in response to the completion of the processing of data, recorded in a region located near the place at which the magnetic tape head is positioned at that time, said region constituting a directory data region (DDR). Further, a directory data memory for recording directory data from the magnetic tape is provided in the magnetic tape subsystem, remote from the tape. At the time of accessing data on the magnetic tape loaded in the magnetic tape subsystem, directory data for the magnetic tape processing is, in response to completion of the processing of data, recorded in the directory data memory in the magnetic tape subsystem.

Magnetic tape data management method and apparatus

An information medium storage and management system includes storage compartments for storing a plurality of information media; a plurality of recording/reproducing apparatus each capable of accessing each of a plurality of information media, each capable of recording at least one file; handling apparatus for mounting a mount information medium on a mount recording/reproducing apparatus and demounting a demount information medium from a demount recording/reproducing apparatus; and a controller for controlling the handling apparatus to select as the mount information medium one of the plurality of information media in accordance with the use history data of each information medium, to select as the mount recording/reproducing apparatus one of unoccupied recording/reproducing apparatus of the plurality of recording/reproducing apparatus, and to cause the mount information medium to use the mount recording/reproducing apparatus for a predetermined time period.

Method and system for storing and managing a plurality of information

In a magnetic storage system including a data conversion unit for performing reading or writing of data from or to a magnetic tape medium, and a system control unit, the data conversion unit has a plurality of electromagnetic transducers which are arranged so as not to overlap with one another in a travel direction of each of a plurality of recording tracks provided on the magnetic tape medium, and performs the reproduction of the data from each reproducing track using one of the electromagnetic transducers a plurality of which are assigned every recording track. In the system control unit, an error included in the regenerative data is detected. When an error is detected, the one electromagnetic transducer which performed the reproduction when detecting an error of the data is switched to another electromagnetic transducer assigned every recording track, thereby to perform the reproduction properly.

Method of reproducing magnetic recording data and a magnetic storage

When the mount and demount operation of information media are achieved between an information medium storage shelf and a plurality of recording/playback apparatuses by use of a plurality of handling devices, in order to execute the operations in a concurrent fashion without causing an interference between the handling devices for an increased operation efficiency, the area of the storage shelf and at least one of the recording/playback apparatuses are respectively subdivided into a plurality of subareas so as to process the obtained subareas by the plurality devices respectively associated therewith.

Automatic storage system and method for information recording media

A circuit for detecting the variation of resistance of a variable-resistance element comprises a pair of grounded-base transistors with their base electrodes provided with different base voltages and with their emitter electrodes connected to both terminals of the variable-resistance element so that the voltage between both terminals of the element is kept constant. The current density of the variable-resistance element does not vary when the resistance of the variable-resistance element varies, whereby the lifetime of the element can be prolonged.

Circuit for detecting variation of resistance of a variable-resistance

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Odawara, Japan

Minoru Kosuge