Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
1998-04-08
2001-10-02
Kim, Matthew (Department: 2186)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C711S112000, C710S068000
Reexamination Certificate
active
06298414
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital data recording method for recording digital data on a recording medium and to a digital data recording medium for saving digital data.
2. Description of Related Art
One of apparatuses for recording and playing back digital data on recording mediums is known as a streaming tape drive. Such streaming tape drives having recording capacities as having recording capacities as large as hundreds of megabytes, although their actual capacity depends on the length of a magnetic tape used as a recording medium. Further such tapes drives are commonly used for backup storage of bulk data which has been saved on a mass recording medium such as a hard disk in a computer. The streaming tape drive is also used for saving image data which is often huge in quantity.
The streaming tape drive is provided with a rotary head operating in a helical scanning mode to record and play back a data on a magnetic tape of the 8-mm VTR format. An example of a conventional streaming tape drives is disclosed in PCT Application No. PCT/JP96/02345 (filed on Aug. 22, 1996) as invented by the same applicant.
The streaming data drive employing a magnetic tape of the 8-mm VTR format as a recording medium includes an input/output interface such as a small computer system interface (SCSI) for data to be recorded or played back.
In recording, data supplied, e.g. from a host computer, is introduced via the SCSI interface to the streaming tape drive. The data may be carried in units of a fixed length data groups and if necessary, compressed by a known data compression method and temporarily saved in a buffer memory. The data released from the buffer memory is then supplied in units of a predetermined data length termed a “group” to a record/playback system where it is recorded on a magnetic tape with a rotary head.
In playback, the data saved on the magnetic recording tape is read out by the rotary head and also saved temporarily in a buffer memory. The data is released from the memory buffer and, when having been compressed in the recording, expanded by a known expansion method before being transferred via the SCSI interface to a host computer.
It is desired that the storage efficiency streaming tape drives or mass data record/playback apparatus be improved in order to allow for the recording of greater amounts of data on a given recording medium. It is also essential that the data saved on the medium is accessed and read at as a great a speed as possible.
SUMMARY OF THE INVENTION
The present invention is directed towards achieving the above requirements and its object is to provide a digital data recording method in which a magnetic tape used as the recording medium for recoding and/or playing back of data in sequences is increased in the efficiency of storage area usage is accessed at a higher speed to read desired one of the data therefrom and a digital data recording medium associated with the method.
A digital data recording method, according to the present invention, where a number of process units of data composed of a plurality of compressed data transmission units produced by compressing fixed length transmission units of data and a dictionary data unit indicative of the information of the compressed data transmission units are allocated to a series of recording units of a fixed length suited for a corresponding recording medium, comprises the steps of: examining whether or not one of the compressed data transmission units in each process unit to be allocated to two adjacent recording units is terminated at the trailing end of a preceding one of the two adjacent recording units for recording the process units into the recording units according to a result of the examination; when the compressed data transmission unit is terminated at the trailing end of the preceding recording unit, ending up the recording of the process unit at the trailing end and reconstructing and recording another process unit which carries the remaining of the compressed data transmission units of the current process unit into the other or succeeding one of the two adjacent recording units; and when the compressed data transmission unit is not terminated at the trailing end of the preceding recording unit, ending up the recording of the process unit at the end of the compressed data transmission unit which extends over the trailing end of the preceding recording unit and reconstructing and recording another process unit which carries the remaining of the compressed data transmission units of the current process unit into the other or succeeding one of the two adjacent recording units.
A digital data recording medium, according to the present invention, where a number of process units of data composed of a plurality of compressed data transmission units produced by compressing fixed length transmission units of data and a dictionary data unit indicative of the information of the compressed data transmission units are allocated and recorded into a series of recording units of a fixed length, is characterized by: when one of the compressed data transmission units in each process unit to be allocated to two adjacent recording units is terminated at the trailing end of a preceding one of the two adjacent recording units, ending up the recording of the process unit at the trailing end and reconstructing and recording another process unit which carries the remaining of the compressed data transmission units of the current process unit into the other or succeeding one of the two adjacent recording units; and when the compressed data transmission unit is not terminated at the trailing end of the preceding recording unit, ending up the recording of the process unit at the end of the compressed data transmission unit which extends over the trailing end of the preceding recording unit and reconstructing and recording another process unit which carries the remaining of the compressed data transmission units of the current process unit into the other or succeeding one of the two adjacent recording units.
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J. Ziv and A. Lempel, “Compression of Individual Sequences via Variable-Rate Coding,” IEEE Transactions on Information Theory, Sep., 1978, pp. 530-536.*
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Chace Christian P.
Frommer William S.
Frommer Lawrence & Haug LLP.
Kim Matthew
Polito Bruno
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