Hitachi, Ltd.

Katsuharu Kakuse

Tokuhiro Tsukiyama

Toshifumi Nishimura

Kazuo Takaragi

Akinobu Shimada

Masafumi Nozawa

Hiroyuki Kitajima

Minoru Kosuge

Takashi Doi

Yasuhiro Ishii

Fujio Fujita

Kiyoshi Yata

Kenichi Kageura

Sadasaburoh Kanai

Syoji Ozaki

Shinpei Saba

Yoshie Kondo

Yasushi Kuba

Kunihiro Itoh

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

In an information processing system having an upper rank apparatus and an external storage device which performs transmission and reception of data between the storage device and the upper rank apparatus, at least one of encryption and decryption of the data by use of an algorithm controlled by a desired data key is performed in the external storage device, while generation, encryption and decryption of the data key are performed on the upper rank apparatus side. By this configuration, the burden of the upper rank apparatus is largely reduced and the secrecy of data stored in the external storage device can be surely kept without spoiling the throughput of the whole system.

File encryption method and file cryptographic system

A magnetic recording subsystem comprises a channel unit, a magnetic recording control unit having a data buffer for temporarily storing data blocks of data transferred from the channel unit and a plurality of magnetic recording units connected to the magnetic recording control unit. When the data is stored into the data buffer, a block number is assigned to each data block. When the data is read from the data buffer and to be stored into a designated magnetic recording unit, the block number supplied from the data buffer and the block number assigned when the data was stored into the data buffer are compared, and then the data is stored into the magnetic recording unit.

Method and apparatus for controlling data writing in magnetic recording

In an optical disc apparatus using an optical disc which has a number of sectors for recording coded information therein, a sector mark formed of a special pattern is previously recorded in each sector at the starting position thereof, to correctly read-out information recorded in each sector. In the case where the optical disc is normally operated, a normal sector mark signal corresponding to each sector mark is detected at a fixed time interval. However, the normal sector mark signal may not be detected for some reasons. A circuit is herein disclosed which generates a pseudo sector mark signal synchronized with the normal sector mark signal. When the normal sector mark signal is not detected, the psuedo sector mark signal is generated, and information recorded in a sector is appropriately processed on the basis of the pseudo sector mark signal. Further, this circuit is provided with circuit means for inhibiting the normal sector mark signal and psuedo sector mark signal from being delivered when the pseudo sector mark signal has been generated a predetermined number of times continuously. However, such inhibition is released when the repetition period of the normal sector mark signal is judged to lie within a predetermined range.

Sector mark signal control circuit for disc apparatus

Method of data compression and restoration wherein an input data string including repetitive data more in number than the specified value is transformed into a data string having a format including the first region where non-compressed data are placed, the second region including a datum representative of a data string section which has undergone the compression process and information indicative of the number of repetitive data, i.e., the length of the data string section, and control information inserted at the front and back of the first region indicative of the number of data included in the first region, said transformed data string being recorded on the recording medium, and, for data reproduction, the first and second regions are identified on the basis of the control information read out on the recording medium so that the compressed data string section is transformed back to the original data string in the form of repetitive data.

Method and system for data compression and restoration

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Hadano, Japan

Katsuharu Kakuse