JPH06139650A - Circulation use type magnetic tape device - Google Patents

Abstract

PURPOSE:To realize the backup of generation with one or plural magnetic tapes by improving the utilizing efficiency of the magnetic tape related to a circulation use type magnetic tape device. CONSTITUTION:A look-ahead head 1 is provided on the magnetic tape device, and MAP information 2 containing the judgment data on propriety using the magnetic tape circulately is recorded on the leader position of the magnetic tape previously. When the lowermost hold generation is warranted based on the MAP information 2 read by the look-ahead head and previously inputted parameter information 3, next generation data is started to be written. When the end (EOT) of volume is detected, and the tape is returned to the leader position, the superscription of the succeeding data of a next generation file is preformed from the leader position of the file of the magnetic tape by recognizing the end position of the invalidatable file by the write end position of next generation remaining data based on the MAP information 2 read again by the look-ahead head. Then, when the end position of the file is detected by the look-ahead head on the way, it is judged that relevant superscription is impossible, and the device enters error processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape device for a computer, and more particularly to a reusable magnetic tape device.

In computer systems of recent years, the utility value of magnetic tapes has declined as the speed and capacity of magnetic disks have increased. However, in view of its large storage capacity, the magnetic tape is being used more and more automatically as a usage pattern, and is often used as a backup of data.

However, when a plurality of data sets (files) are stored on the tape and the data is overwritten for rewriting, the original contents are usually erased and written, so that the erased area and the erased area Since the data is in its original form and there is no guarantee that it will be normal, subsequent datasets (files) will normally not be accessible.

This restriction on use is not only inconvenient to use but also a main cause of reducing the use efficiency of the tape. This is why a magnetic tape device with high usage efficiency is required.

[0005]

2. Description of the Related Art FIG. 4 is a diagram showing a configuration example of a conventional magnetic tape device, FIG. 4 (a) shows a configuration example of a conventional magnetic head, and FIGS. Shows a configuration example of a conventional magnetic tape.

In the conventional magnetic tape device, as shown in FIG. 4 (b1), data is written on the magnetic tape.
The data enclosed by tape marks (marked with a triangle) is regarded as one file, and the last file on the volume is given continuous tape marks (usually two). Files are added from this position, and overwriting is not allowed except for the last file.

As shown in FIG. 4 (a), this is because at the time of writing, the erasing head erases the original data written on the tape, and then the writing head writes the data.
This is because the content of the original data cannot be guaranteed because the next read head checks the written data. In other words, the write control that is not related to the original content is performed, and it is not possible to recognize how far the erase is performed and where the correct original data is stored, and the remaining data is stored in a file that is easy to manage, for example. This is because the unit is not guaranteed. {Refer to Fig. 4 (b2)}

[0008]

Therefore, as shown in FIG. 4 (b1), a plurality of files (first generation and second generation) are recorded in FIG. 4 (b2). As shown, when a new file (third generation file) is written using the area of an unnecessary file (for example, first generation file), the subsequent files are invalid. Therefore, when backing up files,
When files or multiple files are continuously used for generation management, multiple magnetic tape volumes are required, and one volume must be used to store one generation. It was

In view of the above-mentioned conventional drawbacks, it is an object of the present invention to provide a magnetic tape device capable of improving the use efficiency of the magnetic tape and realizing generation backup with one or a plurality of magnetic tapes. Is.

[0010]

FIG. 1 is a diagram for explaining the principle of the present invention, and FIG. 1 (a) shows a structural example of a magnetic head.
FIGS. 1 (b1) and 1 (b2) show examples of using a magnetic tape. The above problems are solved by the magnetic tape device configured as described below.

The magnetic tape device is provided with a read-ahead head 1 and whether or not the magnetic tape can be circulated at the head position of the magnetic tape such as file position, number of records, record length, block length, time stamp, and continuous volume label. It is recognized that the minimum possession generation can be guaranteed based on the MAP information including the determination data of No. 1 is recorded and the MAP information read by the prefetch head 1 and the parameter information that is input in advance when writing the data. Then, start writing the next generation data,
When the end (EOT) of the volume is detected and the head position of the magnetic tape is returned to, the write end position of the remaining data of the next generation is invalid based on the MAP information read by the prefetch head 1 again. Recognizing that it is before the end position (tape mark position) of the file of the previous generation that may be set, the data is overwritten with the remaining data of the next generation from the beginning position of the file of the magnetic tape, When the read-ahead head 1 detects the file end position (tape mark position) in the middle of overwriting with the remaining data of the generation, it is determined that the overwriting is impossible and an error process is performed.

[0012]

Operation: FIG. 1 is a diagram for explaining the principle of the present invention.
Shows an example of the configuration of the magnetic head of the magnetic tape device of the present invention. In the present invention, when the magnetic tape runs as shown in the figure, on the right side of the erasing head, that is, on the magnetic tape. , The pre-read head 1 is added at the fastest position on the tape running so that the original data contents can be pre-read.

Further, as shown in FIGS. 1 (b1) and 1 (b2), next to the conventionally provided volume label, in the present invention, it is determined whether or not the magnetic tape can be circulated. File position (normal file,
It also has a MAP information area for recording the dummy file identification flag), the number of records (total number of records), record length, block length, time stamp, and continuous volume label.

In the example shown in this principle explanatory diagram, generation backup of one file is taken as an example to show how the circular area after the MAP information is used before and after use. .

That is, as shown in FIGS. 1 (b1) and (b2), the magnetic tape is wound when the physical volume end (end: EOT) is reached when the third generation file is to be stored. Returned to the head of the circular use area, whether or not to invalidate the previously recorded first generation file, the parameters previously given by the operator at the time of starting the backup process, and the prefetch head MA pre-read in
Judgment based on P information.

Specifically, since the minimum number of held generations is input to the parameter, the current number of files is recognized from the current MAP information prefetched by the prefetch head 1, and the number of files shown in FIG. In the example of b), for example, since there are two generations, the first generation and the second generation, it can be recognized that the third generation may be written and the first generation may be invalidated.

In the judgment, it should not be invalidated, or it may be invalidated, but in the writing, the end (EOT) of the magnetic tape is detected, the magnetic tape is returned to the head position, and the remaining A theoretical tape mark position is predicted from the write data length and the first-generation tape mark position that may be invalidated (this position is, for example, the number of stored MAP information items (total number of records) and the record length). If it is determined that the remaining data length ≧ the data length up to the tape mark position of the first generation and writing of the third generation is impossible, the backup of the backup is performed. The process is interrupted and the operator is notified.

According to the preliminary judgment, it is recognized that the third generation writing is possible from the theoretical tape mark position, and during the actual writing, the pre-read head 1 makes the following When the tape mark position is detected and it is determined that the remaining data cannot be continuously written (This is because if there is an inaccessible area on the magnetic tape, normally, for example, about 3 inches,
Since the unusable area is instructed as the failure point, there are cases where the actual writing is impossible even though the writing is theoretically possible. } Also interrupts the backup process,
Notify the operator.

When the above conditions are not detected and the first generation can be invalidated, the continuation of the third generation is recorded and the header of the dummy file for considering the empty area as one file after the end. To record.

When the tape is rewound and positioned at the head of the MAP information, the MAP information of the present invention is updated. Therefore, when used for magnetic tape backup or the like, the use efficiency is significantly improved. Further, there is an effect that generation backup can be easily realized with one magnetic tape, for example.

[0021]

Embodiments of the present invention will be described in detail below with reference to the drawings. The above-mentioned FIG. 1 is a diagram for explaining the principle of the present invention.
FIG. 3 is a flow chart showing an embodiment of the present invention.

In the present invention, the magnetic tape device is provided with the read-ahead head 1, and at the head position of the magnetic tape, the file position, the number of stored items, the record length, the block length, the time stamp, the continuous volume label, etc.
MA including data for judging whether or not the magnetic tape can be reused
The means for recording P information is the means necessary for carrying out the present invention. The same reference numerals indicate the same objects throughout the drawings.

The structure and operation of the magnetic tape device according to the present invention will be described below with reference to FIG. 2 while referring to FIG.
In the present embodiment, the backup of the generation of one file will be described as an example, but it goes without saying that the present invention is not limited to this.

First, in the magnetic tape device of the present invention, as shown in FIG.
A read-ahead head 1 is provided to the right of the erase head as shown in (a). However, the running direction of the magnetic tape is
From right to left as shown. Therefore, when the magnetic tape is running, the read-ahead head is first urged to read the contents of the magnetic tape.

Next, as shown in FIGS. 1 (b1) and (b2), in the magnetic tape used in the magnetic tape device of the present invention, the magnetic tape is circulated after the usual volume label. Record the file position (including normal file and dummy file identification flags), number of records (total number of records), record length, block length, time stamp, and continuous volume label that are required to determine whether or not the file can be used. It has a MAP information area.

First, the operator inputs, for example, a volume serial number, read, write category, file name, generation number, number of stored items (total number of records), minimum number of held generations, etc. as parameters {see FIG. 3}. Thereafter, when the magnetic tape is mounted on the magnetic tape device, the MAP information is preread by the prefetch head 1 of the present invention. {Refer to the processing steps 100, 101, 102 of FIG. 2} At this time, based on the pre-read MAP information and the parameter information input in advance, whether the minimum retained generation number can be secured, that is, the first generation It is determined whether or not the second generation file of the second generation can be secured.

Specifically, since the minimum possession generation number is input to the parameter, the current number of files is recognized from the current MAP information prefetched by the prefetch head 1.

In the example of FIG. 1 (b1), for example, since there are two generations, the first generation and the second generation, it is possible to write the third generation and invalidate the first generation. Beforehand,
That is, it can be recognized before the actual writing process of the third generation. However, if a write error occurs,
The judgment cannot be said to be absolute. {Refer to processing step 103 in FIG. 3} In the judgment, if the previous generation file should not be invalidated {refer to processing step 103 in FIG. 3}, or may be invalidated (that is, may be overwritten). However, the remaining write data length of the next generation and the first generation tape mark position that may be invalidated (this position is, for example, as described above,
The theoretical number of tape marks can be predicted from the number of stored MAP information items (total number of records) and the record length}, and the remaining data length ≧ the data length up to the tape mark position of the first generation If it is determined that the third generation writing is impossible (see processing steps 103, 104 and 105 in FIG. 3), the backup processing is interrupted and the operator is notified. {Processing steps in FIG. 3
Refer to 114} In the above judgment, it is recognized that the next generation writing is possible, and as shown in FIG. 1 (b1), the third generation writing is performed, and the tape mark position of the second generation file (indicated by a triangle). When the physical volume end (end: EOT) is reached, the magnetic tape is rewound and returns to the beginning position.
The remaining write data length of the third generation, and the first generation tape mark position that may be invalidated (this position is, for example, as described above, the number of stored MAP information items (total number of records) and records) The theoretical tape mark position can be predicted from the length}, and it is recognized that the third generation writing is possible from the theoretical first generation tape mark position. If the pre-read head 1 detects the position of the next tape mark and determines that the remaining data cannot be written in the middle of writing to the disk (as described above, operation of the magnetic tape device In the state, if there is an inaccessible record, for example, about 3 inches is instructed as a non-writable area, so writing is not always possible according to theory. Possibly} also suspends processing of the backup, and notifies the operator. {Refer to processing steps 103, 104, 105, 106, 111, 114 in FIG. 3} If the condition that the next-generation writing is not possible is not detected and all the files of the first generation can be invalidated, the continuation of the third generation is recorded. Then, after the writing is completed, the header of the dummy file for recording the empty area as one file is recorded. {Processing step 112 of FIG.
Reference} When the magnetic tape is rewound and positioned at the head of the MAP information, the MAP information of the present invention is updated. For example, a continuous volume label and the like are added, and the dummy file position and the like are written. {Refer to processing step 113 in FIG. 3} As described above, in order to guarantee the file of the minimum possession generation, the read-ahead is required at the time of writing. Therefore, the above-described read-ahead head is provided in the present invention.

Next, in the case of the read operation, if the file (the third generation file in the above example) is divided as described above, for example, the following read method is used to increase the speed. I do.

Usually, when the file is divided,
Subsequent data is located at the head of the magnetic tape, and data originally located at the front is written after the magnetic tape. Therefore, when reading the data of the divided file, it is at the head of the magnetic tape. Sequential data is first stored in a work file (not shown), the file before the divided file located at the end of the magnetic tape is read, then the data of the work file is read, and the data is divided. Connect the existing files to the original undivided state. {Processing steps 106, 107, 108, 1 in FIG. 3
As described above, in the present invention, the read-ahead head 1 and the MAP information for determining whether or not the magnetic tape can be reused are provided on the magnetic tape, and the backup When the process is started, it is determined in advance whether or not the next generation file can be written by the above parameters given by the operator in advance and the MAP information prefetched by the prefetch head 1. If it is recognized that there is an error process to notify the operator, circular writing of the file is possible, writing of the current generation file is started at the position next to the file of the previous generation, and the volume When the end (EOT) is detected, before returning to the front end of the magnetic tape and starting the subsequent writing, the pre-read head pre-reads the MAP information and crushes the front end. If it is possible to predict the tape mark position of a good generation file and write the next-generation file data that is about to be written, perform the next-generation writing, and during the actual writing. The feature is that when the tape mark is detected, the operator is notified that the writing has failed.

[0031]

As described above in detail, according to the magnetic tape device of the present invention, since the magnetic tape can be circulated and used, when the magnetic tape is used for backup or the like,
Use efficiency is significantly improved. Also, 1 generation backup
This can easily be achieved with one or more magnetic tapes.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is a flowchart showing an embodiment of the present invention (No. 1).

FIG. 3 is a diagram (No. 2) showing a flow chart of one embodiment of the present invention.

FIG. 4 is a diagram showing a configuration example of a conventional magnetic tape device.

[Explanation of symbols]

 1 Read-ahead head Volume label MAP information △ Tape mark 100-114 Processing steps

Claims (1)

[Claims] 1. A magnetic tape device is provided with a read-ahead head (1), and MAP information () including data for judging whether or not the magnetic tape can be reused is recorded at the head position of the magnetic tape, and the data is recorded. At the time of writing, when it is recognized that the minimum possession generation can be guaranteed based on the MAP information () read by the prefetch head (1) and the parameter information () input in advance, next-generation data Writing is started, the end (EOT) of the volume is detected, and when the head position of the magnetic tape is returned to, the read-ahead head (1) is read again.
The magnetic tape is recognized based on the MAP information () read in step 1) that the write end position of the remaining data of the next generation is before the end position of the previous generation file that may be invalidated. When the end point of the file is detected by the prefetch head (1) during the overwrite of the remaining data of the next generation, writing is performed by overwriting the remaining data of the next generation of data from the beginning position of the file A magnetic tape device of a reusable type, characterized in that it is determined that the overwriting is impossible and an error process is started.