JP3705048B2 - Data writing control method for magnetic tape device and magnetic tape device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic tape device, and more particularly to an error retry method when a write error occurs in a magnetic tape device.
[0002]
[Prior art]
Regarding the data write control method in the magnetic tape device, according to the standard such as JIS, when a write error occurs when writing data, the tape is rewound and the position where the write error occurred (from a certain interval according to the standard) ) Write the erase pattern, skip the area on the tape where the error occurred, and perform the write process again.
[0003]
If a write error occurs again in the write process again, the erase pattern is similarly written in the area on the tape where the error has occurred, the error area on the tape is skipped, and the write process is performed again. The above rewrite process is performed a specified number of times (the number of continuous write of the erase pattern is determined by the standard). If the error is still not recovered, a write error is reported to the control device and the process is interrupted.
As the above-mentioned JIS standard, there is JIS_X6135.
[0004]
In Japanese Patent Laid-Open No. 8-45520, as a method of avoiding a write error,
(1) Change the size of the write data block.
(2) The density ID pattern length is changed.
(3) Write the erase pattern after writing the volume ID at the tip of the tape.
(4) Change the length of writing the erase pattern.
(5) Write a dummy block.
(6) The tape is moved back and forth around the error occurrence position.
(7) Change the amount of air blown from the head.
Various error remedy methods are presented.
[0005]
[Problems to be solved by the invention]
Causes of writing errors when writing data on a magnetic tape device include:
1. Scratches on the tape medium The main factor is adhesion of garbage.
[0006]
When there is a writing error due to a scratch on the medium, the writing error can be saved by a rewriting method according to the conventional technique. In other words, the scratches on the tape medium are usually very small, so if you write the erase pattern and skip the location of the tape medium where the error occurred, the scratch position will be removed, so rewriting the data Can be written correctly.
[0007]
However, in the case of a write error caused by dust, there is a possibility that the write error cannot be saved by the error retry method according to the conventional technique. Reading and writing data to and from the tape medium is always performed by contacting the tape medium and the magnetic head. Further, dust adhering to the tape medium is usually removed by a tape cleaner installed in front of the magnetic head. However, sticky debris may not be removed with this tape cleaner. Even when the tape is moved back and forth around the position where the error occurred or the air blowing amount of the head is changed as in the publicly known example of Japanese Patent Laid-Open No. 8-45520, sticky dust cannot be easily removed. .
[0008]
Therefore, sticky dust sticks to the magnetic head during the writing operation and accumulates around the head. This contamination of the magnetic head may always cause a write error. In this case, since the error retry operation is always executed, there is a problem that the processing time becomes very long. There is also a problem that the erase pattern write area becomes long (maximum) due to error retry. This wastes a useless area (erase pattern writing area), so that the storage capacity becomes inefficient. Further, since the retry is performed with the head still dirty, there is a possibility that the writing error cannot be saved even if the retry is performed over a long time.
[0009]
An object of the present invention relates to a rewriting method at the time of writing error at the time of data writing in a magnetic tape device, and a data writing control processing system capable of coping with a writing error due to adhesion of sticky dust to a magnetic head Another object of the present invention is to provide a write error retry method and a magnetic tape device using them.
[0010]
At the same time, it is intended to shorten the time required for retry by providing a simple error retry method.
[0011]
Furthermore, by saving the write error, it is possible to reduce a useless erase pattern area on the tape and to effectively use the tape storage capacity.
[0012]
[Means for Solving the Problems]
In order to achieve the object of the present invention, when a write error occurs in the data writing process to the tape medium, the data block is repositioned at the head of the data block where the write error has occurred. This BSB (Back Space Block) operation is performed in a state where the air blowing from the head is stopped and the tape and the magnetic head are in close contact with each other. In the case of a write error due to sticky dust, there is an effect of moving or dusting off dust attached to the magnetic head by the BSB operation of the tape with air blowing from the head stopped. Thereafter, the data can be reliably written by performing the data rewriting process. If the write error is not recovered even if the rewrite including the BSB operation is performed a specified number of times, it is determined that the cause of the write error is not a dust collected around the magnetic head but a scratch on the tape medium.
[0013]
In this case, after repositioning at the head of the data block in which the error has occurred in the BSB operation, the erase pattern is written as in the conventional case to skip the area in which the error has occurred on the tape medium. Thereafter, data rewrite processing is performed. Write errors caused by scratches on the tape medium can be saved by this means. This simple retry operation also has the advantage of not requiring a long time for the retry.
[0014]
The write / retry control according to the present invention is characterized in that the write error is not relieved by the erase pattern write first. This is because if the error retry by writing the erase pattern is performed first, if it is caused by sticky dust, not only will it take a long time to retry, but the error may not be saved.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a data write control flowchart according to the data write control processing method of the magnetic tape apparatus of the present invention. FIG. 2 shows a general configuration (component arrangement) of a magnetic tape device (tape deck) and a structure of a tape cleaner. FIG. 3 shows the state of the magnetic head to which sticky dust is attached and the effect of the present invention. FIG. 4 shows a logic circuit configuration of the magnetic tape subsystem.
[0016]
FIG. 5 to FIG. 11 show the writing format when writing by the conventional method and the writing when writing by using the data writing control processing method of the present invention when sticky dust adheres to the magnetic head. Indicates the format.
[0017]
12 and 13 show the data writing format when the tape medium is damaged when the data writing control processing system of the present invention is used.
[0018]
FIG. 1 is a flowchart of data write control according to the present invention. When a data write request is requested from the host device such as a CPU to the control device of the magnetic tape device (1), data is written to the magnetic tape (2). If there is no error as a result of writing the data (3), the data write request ends normally, and the next request from the host device is waited (14). If a write error is detected, the tape is rewound to the beginning of the area (Block) where the data has been written (4).
[0019]
At this time, air blowing from the magnetic head is stopped. Then, data is written again (5). A write error is checked (6). If there is no error, the data write request is terminated normally and the next request from the host device is waited (14). If a write error is detected again, the number of BSB operations with the air blowing stopped is checked (7). If it is within the set number of times, the data is again written at the beginning of the area (Block). The tape is rewound with the air blown from the head stopped (4), and data is written again from there (5).
[0020]
If the write error is not recovered even if the above (4) to (7) are performed for the set number of times (when the set number is exceeded), the tape is rewound to the head of the area (Block) in which the data is written (8 ) Write the erase pattern and skip the area where there was an error. After that, the data is rewritten (9). A counter indicating that the erase pattern has been written is added to manage the number of times the erase pattern is continuously written (10). (The number of times the erase pattern is continuously written is determined by standards such as JIS and is 50.) Here, the data written following the erase pattern is checked for the presence of a write error ( 11). If there is no error, the data write request ends normally and waits for the next request from the host device (14). At this time, the erase pattern write counter is reset.
[0021]
If a write error is detected again, the number of consecutive writes of the erase pattern is checked (12), and if it is within the allowable number, the tape is rewound to the head of the area (Block) where data has been written again ( 8) The erase pattern is written from there, and the area with the error is skipped. After that, the data is rewritten (9). A counter indicating that the erase pattern has been written is added (10), and the number of times of continuous writing of the erase pattern is added. If the write error is recovered within the prescribed number of times of continuous write of the erase pattern, the data write request is terminated normally and the next request from the host device is waited (14). The erase pattern write counter is reset. If the write error is not recovered, the job is interrupted, the write error is reported to the host device, and the process is terminated (14).
[0022]
FIG. 2 shows a general structure of a tape deck and a structure of a tape cleaner. When the magnetic tape is loaded into the tape deck 20, the tape (leader block) is automatically loaded onto the machine reel 26. Between the magnetic tape file reel 21 and the machine reel 26 are a tape tension buffer 22, a tape cleaner 23, a head guide 24, and a magnetic head 25. The tape cleaner 23 has a role of removing dust attached to the magnetic tape. As shown in Fig. 2, it has a structure that scrapes off the dust on the tape surface. In order to remove the dust efficiently, negative pressure air (suction) is applied (31) so that the tape medium is in close contact with the tape cleaner. (32).
[0023]
The magnetic head 25 has an air outlet and normally blows air during a locating operation other than writing / reading on the tape so that the tape medium is lifted (not brought into close contact) from the magnetic head. Air to the tape cleaner 23 and the magnetic head 25 is sent from an air pump 27.
[0024]
FIG. 3 shows a state of the magnetic head to which sticky dust is attached. Sticky dust tends to adhere to the vicinity of the tip of the magnetic head (41). In the conventional operation, in the tape locating operation other than the data writing / reading, air is blown out from the head so that the tape and the head are not brought into contact with each other (42). This is to prevent unnecessary wear of the head and the tape medium itself.
[0025]
However, data writing / reading operations with sticky dust remaining on the head are unlikely to be saved no matter how many retries are performed. Therefore, if an error occurs, first suspect the head is dirty. When the tape is rewound by the BSB command for data rewriting (45), the air blowing from the head is stopped and the tape medium and the head are controlled to be in close contact (44). Then, the sticky dust moves in the tape running direction and disappears near the tip of the head (43). Some debris that has moved will be blown away in a certain amount of mass.
[0026]
FIG. 4 shows the configuration of the logic circuit of the magnetic tape subsystem. The write data is sent from the CPU 72 to the channel IF 80 of the magnetic tape subsystem controller (MTC). In MTC, write data is sent from the drive IF 83 to the magnetic tape unit (MTU) from the channel IF 80 via the data compression 81 and data buffer 82. The microprogram for controlling the MTC is read from the floppy disk (FD 84) and loaded into the program memory 86. With this program, the MTC microprocessor (MP85) controls each logic circuit of the MTC.
[0027]
On the other hand, the MTU is also controlled by a microprogram. The program is shared and stored in the FD 84 of the MTC, and is stored in the program memory 88 of the MTU via the MTC drive IF 83 and the MTU drive IF 96.
[0028]
The MTU includes two processors: a servo microprocessor (MP89) that controls the machine reel motor 90, the file reel motor 91, and the like, and an MTU microprocessor (MP87) that controls the other I / O control 92, the air pump 91, and the like. Are installed and control the MTU in cooperation with each other while communicating with each other.
[0029]
Write data from the MTC is written to the tape via the magnetic head 94 from the WR / RD amplifier 95 via the drive IF 96 of the MTU. The read data is sent to the CPU 72 through this reverse path.
[0030]
The tape deck 20 of FIG. 2 is controlled by the logical configuration of the MTU of FIG. 4, and the data write control microprogram of FIG. 1 is executed by the MPU MP87 and the servo MP89.
[0031]
The data writing procedure and the format on the tape in the apparatus configuration of FIG. 2 will be described with reference to FIGS. When the cartridge tape is loaded into the tape deck 20, the cartridge tape itself becomes the foul reel 21, and is wound around the machine reel 26 along the tape traveling path (30). The tape cleaner 23 in the middle of the travel path (30) serves to remove dust adhering to the tape. As shown in FIG. 2, it is shaped to scrape off dust, and the inside is hollow and sucks out air. As a result, the tape cleaner and the tape medium are brought into close contact with each other to reliably remove dust.
[0032]
If it is about normal garbage or dust, it will be sucked out by this tape cleaner and will not stain the head. However, in the case of sticky garbage, it sticks to the edge of the tape cleaner. If it sticks to some extent, it will start sticking to the head guide 24 or the magnetic head 25 located at the tip of the tape cleaner. Adhesive dust cannot be sucked out with tape cleaner air.
[0033]
The magnetic head 25 has a structure that blows out air, and when locating the tape (other than reading and writing data), the air is blown out so that the tape medium does not adhere to the head, but it adheres when reading and writing data. For this reason, when reading / writing is repeated, sticky dust accumulates on the head. This state is shown in FIG. Garbage accumulates at the top of each of the magnetic head, WR head 47 and RD head 48 (41).
[0034]
The case where data is written by the conventional method in this state is shown in FIGS. In FIG. 5, an attempt is made to add BLKb (53) after IBG (52), but writing fails because the magnetic head 25 is dirty with sticky dust. As a result of the retry, an erase pattern (hereinafter referred to as ERG) a (54) and IBG (55) are written at the position of BLK (54). The BLKb (56) is rewritten following the IBG (55) (FIG. 6), but again fails because the dirt attached to the magnetic head 25 has not been removed. Thereafter, in this state, the erase pattern is written a specified number of times, and the specified number of continuous write of the erase pattern is reached, the retry is completed, and the write is ABEND (FIG. 7).
[0035]
Data writing according to the method of the present invention is illustrated in FIGS. As with the conventional method, in FIG. 8, I try to add BLKb (53) next to IBG (52), but writing fails because the magnetic head 25 is dirty with sticky dust (FIG. 8). 9). Therefore, the BSB operation of the tape by retrying is performed in a state where the blowing of air from the magnetic head 25 is stopped. Then, the dust on the head moves in the running direction of the tape as shown in (43) of FIG. After the BSB operation, the tape is positioned at the position where BLKb (53) is written (FIG. 10), and BLKb is rewritten (FIG. 11). Due to the BSB operation in which the air is stopped, the sticky dust on the magnetic head 25 has moved from the head tip and succeeded in writing BLKb (64) (65). Here, when the writing of BLKb again fails (when an error occurs again), as shown in the flowchart of FIG. 1, the BSB operation in which the air is stopped within a specified number of times is repeated (7), and the magnetic head Try to remove the garbage.
[0036]
According to the above operation, data can be written correctly even when sticky dust adheres to the magnetic head.
[0037]
Next, the data writing procedure when the tape medium is damaged will be described with reference to FIGS.
[0038]
In FIG. 12, a data block (hereinafter referred to as BLK) a (51) and an accompanying block delimiter: Inter block Gap (hereinafter referred to as IBG) (52) are already written on the tape, followed by BLKb (54). However, there is a scratch (71) at the place where BLKb (54) is written. When BLKb (54) is written in accordance with the data write control system of FIG. 1, an error is detected by the write error check (3) by the scratch (71), and it is determined that sticky dust is attached, and air is blown out. The BSB retry operation (4) to (7) depending on the stop is performed a specified number of times.
[0039]
However, since the cause of the write error depends on the scratch on the tape medium, the retries (4) to (7) cannot be saved. Once the specified number of retries is exceeded, the tape is rewound (8) and positioned immediately after IBG (52). In FIG. 13, the erase pattern (54) is written (9), and the accompanying IBG (55) is written. Subsequently, BLKb is written again at the position (56). Since there is no scratch in the area where BLKb (56) is written, no error occurs in error check (11), and JOB ends normally (13).
[0040]
According to the above procedure, even when there is a scratch on the tape, the data can be written correctly by the write control processing method according to the present invention.
[0041]
By using the data write control processing method as described above, when a data write error occurs, it not only saves the write error due to sticky dust adhering to the write error medium to be taped but also due to scratches on the tape medium. Even if a write error occurs, it is possible to save the error as well.
[0042]
Further, when such a tape is ejected from the drive, a “head cleaning request” message is displayed on the message panel of the drive, and the user can be prompted to clean the magnetic tape device with the cleaning tape.
[0043]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to rescue the data write error resulting from adhesion of the sticky refuse to a tape medium in the data write in a magnetic tape apparatus. In addition, the time required for error retry can be shortened. Since the area where the erase pattern is written can be reduced, the loss of the storage capacity of the tape can be minimized.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a data write control method of a magnetic tape device according to the present invention.
FIG. 2 is a diagram showing a general configuration (component arrangement) of a magnetic tape device (tape deck) and a structure of a tape cleaner.
FIG. 3 is a diagram showing the situation of a magnetic head to which sticky dust is attached and the effect of the present invention.
FIG. 4 is a diagram showing a configuration of a logic circuit of a magnetic tape subsystem according to the present invention.
FIG. 5 is a diagram showing a format when data is written by a conventional method when sticky dust is attached to the magnetic head.
FIG. 6 is a diagram showing a format in a state where a retry is performed once by a conventional method when sticky dust is attached to the magnetic head.
FIG. 7 is a diagram showing a format in which an erase pattern is written to a limit defined by a standard by a conventional method when sticky dust is attached to a magnetic head.
FIG. 8 is a diagram showing a format to write data when sticky dust is attached to the magnetic head.
FIG. 9 is a diagram showing a format in which data is written while the head is dirty when sticky dust adheres to the magnetic head.
FIG. 10 is a diagram showing a format in a state where a BSB operation is performed by stopping air blowing from the magnetic head by data write control according to the present invention when sticky dust adheres to the magnetic head. .
FIG. 11 is a diagram showing a format in which data is rewritten after a BSB operation is retried in the data write control according to the present invention when sticky dust is attached to the magnetic head.
FIG. 12 is a diagram showing a format before data is written when there is a scratch on the tape medium.
FIG. 13 is a diagram showing a format in which data is written using the data write control method according to the present invention when there is a scratch on the tape medium.
[Explanation of symbols]
20: Tape deck 23: Tape cleaner 25: Magnetic head 27: Air pump 31: Air inlet 40: Air outlet

Claims (4)

Air is supplied to a surface including a magnetic head, a file reel, and a machine reel, a tape running path for running the magnetic tape on the magnetic head, an air pump, and a surface where the magnetic head and the magnetic tape face each other. A data writing control method for a magnetic tape device having an air blowing pipe,
Writing the data by running the magnetic tape in a state where the magnetic tape is levitated above the magnetic head by air supplied from the air blowing pipe;
If a write error occurs during data writing, stopping the air supply and rewinding the magnetic tape;
Rewriting the data;
When an error occurs in the rewriting, if the number of times data is rewritten with respect to the data is less than a specified number, the step of rewinding the magnetic tape and the step of rewriting the data are repeated. Data write control method for magnetic tape device. When an error occurs in the rewriting, when the number of times data rewriting has been performed on the data exceeds the specified number, the step of rewinding the tape;
Writing an erase pattern; and
2. The data writing control method for a magnetic tape device according to claim 1, further comprising a step of rewriting data. Air is supplied to a surface including a magnetic head, a file reel, and a machine reel, a tape running path for running the magnetic tape on the magnetic head, an air pump, and a surface where the magnetic head and the magnetic tape face each other. An air blowing pipe; and a control unit that controls the air pump, the file reel, and the machine reel, and the magnetic tape is moved from above the magnetic head by air supplied from the air blowing pipe when the magnetic tape is running. In the magnetic tape device that floats
The control unit, when an error occurs during data writing, stops supplying air from the air blowing pipe, rewinds the magnetic tape, and rewrites the data. apparatus. 4. The magnetic tape device according to claim 3, wherein a write error occurs even if the rewinding of the magnetic tape and the rewriting of the data are repeated a predetermined number of times while the supply of air from the air blowing pipe is stopped. In the case, the magnetic tape device is characterized by writing an erase pattern.

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