Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data in specific format
Reexamination Certificate
2001-03-08
2002-07-23
Faber, Alan T. (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data in specific format
Reexamination Certificate
active
06424478
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for recording and reproducing digital data and a method for the same, and more particularly to an apparatus for recording blocked digital data on a magnetic tape and a method for the same.
2. Description of the Related Art
In recent years, various kinds of apparatuses for recording and reproducing digital data have been widely applied with the advancement of the technology for recording and reproducing digital data. As a record medium, a hard disk, an optical disk, a magnetic tape, and the like are used. Among them, the magnetic tape is more practical and superior in storage capacity, changeability, and price (in a unit cost of capacity), compared with other record media.
Data to be recorded on a magnetic tape is mainly classified into two kinds of data: data transferred and recorded by a host such as a computer and data automatically added (additional data) by an apparatus for recording and reproducing. The additional data includes information concerning a leading edge and a trailing edge of a recording region on a magnetic tape, information concerning the delimitation of blocks formed therein, an address indicating the position therein, information for error detection or error correction, etc. It is convenient for the host to utilize information concerning a name, an attribute, a size, and the like of data during recording, reading, or searching for the data. Such information is referred to as management data in the present specification.
The data transferred by the host is recorded after being divided into blocks having a predetermined size. For example, in the case of a usual computer, the data is divided so as to have 512 bytes per block. Each block is the minimum unit of the magnetic tape in which data can be recorded. Data divided into a predetermined size by the host is referred to as blocked data (herein, blocked data means a “blocked data” unit or “data block”). Thus, the blocked data becomes the minimum unit for recording on the magnetic tape. Furthermore, instructions (marks) for searching data can be recorded on the magnetic tape. The blocked data and marks can be recorded with respective numbers assigned thereto.
Some blocked data can be combined to be recorded as grouped data (herein, grouped data means a “grouped data” unit or “data group”).
FIG. 34
shows an example of grouped data recorded by a conventional apparatus for recording and reproducing digital data. This example shows a DDS format using a digital audio tape-recorder (DAT). One group of the grouped data include 126632 bytes. Each blocked data is arranged from the leading edge of the grouped data.
Information concerning the grouped data (management data) G is positioned in a group information table placed in 32 bytes of the trailing region of the grouped data. Information concerning each blocked data (management data) B
1
, B
2
, . . . indicating the size and the like of each blocked data are arranged in the direction from a portion right before the group information table to the leading edge of the grouped data. The information B
1
, B
2
, . . . concerning each blocked data respectively have a fixed length.
In the DDS format, data is recorded and reproduced as follows:
In a random access recording and reproducing apparatus, by designating the number assigned to each block (i.e., absolute addressing), data corresponding to the block with that number assigned can be read or recorded. Likewise, by absolutely addressing the number assigned to each mark, data can be reproduced from the position of the mark with that number assigned.
In a sequential recording and reproducing apparatus which does not perform random access, data is recorded in the order in which the blocks are arranged or in a predetermined order. Likewise, data is read in the order in which the blocks are recorded. In the sequential recording and reproducing apparatus, the position of the recorded blocks is relatively addressed (for example, a block following four blocks after a certain block).
As described above, data is recorded or read by relatively or absolutely addressing a block.
Hereinafter, a searching method in a conventional DDS format will be described.
FIG. 35
schematically shows grouped data in the conventional DDS format. As shown in this figure, the number of a block whose recording is first started in a group and the number of blocks whose recording is started in the group are recorded in a subcode region on a group basis. The block No. is represented by g, and the number of the blocks is represented by m. Hereinafter, simply referred to as numbers g and m. The subcode region is a region of the track where data can be reproduced even during searching.
When the numbers g and m are obtained for a group during searching, it is found that the recording of the blocks with the numbers g to g+m−1 is started in the group. By using this, the group in which the recording of a desired group is started is found, and a desired block is reproduced. Likewise, the number h (h
1
in the figure) of a mark whose recording is first started in a group and the number k of marks whose recording is started in the group are recorded in the subcode region of the group. In the case where the numbers h and k are obtained for a certain group during searching, it is found that the recording of the marks with the numbers h to h+k−1 is started in the group. By using this, the group in which the recording of a desired mark is started is found, and a desired block in a position designated by the mark can be reproduced. Alternatively, data searching can be conducted by recording, in the subcode region, the number of a block whose recording is first started in a group and the number of a block whose recording is last started in the group.
FIGS. 36A
to
36
D show the patterns of track groups recorded in the conventional DDS format. A magnetic tape runs in the direction indicated by an arrow in FIG.
36
A. Grouped data to be recorded is subjected to a predetermined signal processing to form a data track group D
1
. As shown in
FIG. 36B
, the data track group D
1
is recorded on the magnetic tape together with amble track groups A positioned before and behind the data track group D
1
(i.e., a preamble track group and a postamble track group) and a data end track group E.
Overwriting of data is conducted as follows:
First, the data end track group E is searched to detect the last-recorded position. Then, recording of data is started from the trailing edge of the postamble track group A positioned before the data end track group E. As a result, the data end track group E which has been recorded is deleted and only a latest-recorded data end track group E is left on the magnetic tape.
FIG. 36D
shows the pattern of track groups in which data track groups D
2
to D
4
shown in
FIG. 36C
are recorded in addition to the data track group D
1
.
In order to prevent a data track group from being positioned right before the track at which the additional recording is started, the previously recorded postamble track group A is left on the magnetic tape. The reason for this is that the track, right before the track at which the additional recording is started, has its width cut away by the additional recording, increasing the frequency of error occurrence.
Furthermore, as shown in
FIG. 37A
, in the conventional DDS format, information concerning the entire magnetic tape (tape management data) is recorded in a system area positioned in a leading region of the magnetic tape. In the DDS format, one or two data regions called a partition can be assigned on the magnetic tape for convenience of data management.
The leading region of each partition is assigned as a system area corresponding to the partition, and information concerning the use record of the partition (i.e., system log) is recorded in a subcode region of the system area (see FIG.
37
B). Data is recorded with a fixed-length in the subcode region. In the case where one partition is assigned
Hamai Shinji
Iketani Akira
Imai Fumikazu
Matsumi Chiyoko
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