JPS6154007A - Erasure recovery system of magnetic tape device - Google Patents

Abstract

PURPOSE:To perform accurate erasure and improve the quality of re-erasure by performing repositioning control over the re-erasure on the basis of the confirmation result of the identification number of a last data block and the counted value of a backward run distance. CONSTITUTION:A block read control circuit 21 put a magnetic tape device 1 in forward run operation according to an erasure indication from a host device, an erasing circuit 20 flows an erasure current to both heads, and the circuit 21 monitors read data simultaneously. When a noise is detected, the run of a magnetic tape is stopped and when the number of times of re-erasure is smaller than a specific value, the re-erasure is performed, and the circuit 21 puts the device 1 in backward run operation and actuates a back space counter 22 to count the length from the noise detection position to the rear end of the last block. Then, the circuit 21 puts the device 1 in forward run operation and sets the counted value of the counter 22 in the circuit 20, thereby starting the era- sure of the area from the noise detection position to the end part of the last block.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a one-sided type of glue recovery when noise is detected during an erase operation performed at the time of a write error in a magnetic tape device, and in particular to a method for performing re-erase. This article relates to an erase recovery method for magnetic tape devices.

Magnetic tape devices are widely used as external storage devices for computers. In a magnetic tape device, read/write operations are carried out serially on a magnetic tape, and at the time of writing, writing of write data is checked by read-after-write. If an error occurs in this write check, the magnetic tape device notifies the host device of the error, and the host device sends a bank space (Back 5pace) command to reverse the magnetic tape and rewrite the data. If an error is detected during writing, the block is erased so that it is no longer used.

[Conventional technology]

FIG. 5 is an explanatory diagram of the conventional erase recovery method. As shown in FIG. 5(A), when a write command is received from a host device (computer), the read/write head H1 is writing an N+1 block to the magnetic tape MT. When an error is detected, the error is notified to the higher-level device. The host device gives a bank space command to the magnetic tape device, moves the magnetic tape backwards as shown in FIG. 5(B), and turns the read/write head H1 into
Position it at BG (interblock gap). Next, the host device issues an erase command, causes the magnetic tape MT to run in the space direction, and erases the erase head H2.
An erase current is applied to the read/write head H1, and the fifth
As shown in Figure (C), the magnetic chip 7" MT is magnetized in a certain direction. During this erase operation, the read/write head H1 reads the magnetic tape MT, determines whether or not the successive patterns are noise patterns, and To detect.

If the magnetic tape MT is uneven due to bending or has dust, etc., a noise pattern will occur even after erasing.
When such a noise pattern is detected as shown in FIG. 5(D),
Stops tape running and notifies the higher-level device.

[Problem that the invention seeks to solve]

In the conventional erase recovery method, when noise is detected during erasing, it is immediately notified to the higher-level device and the higher-level device is asked to make a decision, so even if noise occurs due to the presence of dust, etc., it cannot be determined by the higher-level device. The magnetic tape needed to be replaced. In order to solve this problem, it is possible to instruct re-erase from the host device, but if the commands from the host device are only write commands, read commands, erase commands, and backspace commands, the backspace for re-erase is Since the space is controlled by IBG detection, there is a problem that positional deviation is likely to occur (there is a risk of destroying the previous correct data block (N in the figure)).

[Means for solving problems]

SUMMARY OF THE INVENTION The present invention provides an erase recovery method for a magnetic tape device that is capable of re-erasing without instructions from a host device and also performing an accurate erase operation to prevent destruction of correct data blocks.

For this reason, the present invention uses magnetic data in response to an erase instruction.

It has an erase circuit that causes the head to erase the contents of the magnetic tape, and a control circuit that monitors the read data from the magnetic head and controls the running of the magnetic tape, and eliminates noise from the read data during the erase operation. An erase recovery method for a magnetic tape device in which the control circuit instructs the erase circuit to re-erase when detecting the erasure circuit, wherein a counter is provided to count the traveling distance or time of the magnetic tape in the backward direction during the re-erase. , upon the noise detection, the control circuit causes the magnetic tape to run in the backward direction until the block identification number of the previous block on the magnetic tape is confirmed, and then causes the magnetic tape to run in the forward direction for re-erasing;
It is characterized in that a re-erase operation is performed based on the value counted by the counter.

[Effect]

In the present invention, when noise is detected during the erase operation, the control circuit instructs the erase circuit to re-erase and automatically executes the re-erase without any instruction from a higher-level device. The precision of the re-erase is improved by confirming the identification number of the data block and re-erasing based on the count value of a counter that counts the running ratio l1lit (or time) in the bank direction.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is a block diagram of one embodiment of the present invention, in which 1
2 is a magnetic tape device having the above-mentioned read/write head H1, erase head H2, and a magnetic tape drive mechanism (not shown); 2 is a magnetic tape control device;
20 is an erase circuit that controls the magnetic tape device 1 according to instructions from a host device (computer);
Both heads H1 and H respond to erase instructions from the host device.
2, which controls the flow of erase current to
21 is a block read control circuit which monitors the read data read from the read section (read head) of the head H1, identifies whether it is a noise pattern or another pattern, and controls the running of the magnetic tape; 23 is a backspace counter, which counts the traveling distance (or time) of the tape during back-travel during re-erasing; 23 is a block register; the block identification number (hereinafter referred to as BID) of the data block immediately before the erase area; ), and 24 is a comparison circuit that compares the read data from the block read control circuit 21 with the BID of the block register 23.

Next, the operation of the embodiment configuration in FIG. 1 will be explained using the time chart diagram in FIG. 2, the operation explanatory diagram in FIG. 3, and the processing flow diagram in FIG. 4.

■ First, when an erase instruction is given from the higher level, the erase operation is performed. Then, the control circuit 21 causes the magnetic tape device 1 to run in the forward (FW) direction, and the erase circuit 2
0 gives an erase signal to the magnetic tape device 1, causing an erase current to flow through both heads H1 and H2. During this time, the control circuit 21 monitors the read data from the head node H1, determines whether it is a noise pattern, and if noise is detected, stops the running of the magnetic tape.

■ Conversely, if no noise is detected, run the specified distance,
Stop running the magnetic tape and end the erase process.

■ When noise is detected in step ■, the control port 21 checks the number of re-erases, and if the number of re-erases is greater than a predetermined value, no further re-erase is performed and an error is sent to the upper level. Notify and terminate.

■ On the other hand, if the number of times of re-erase is within a predetermined value, re-erase control is performed, that is, as shown in FIG. 3(A), the control circuit 2
1 is the back side of the magnetic tape device 1.

The robot moves in the direction (backspace) and activates the space counter 22.

The control circuit 21 controls the head H generated by this back running.
Monitor the read data from 1 and read the BO of the previous block N.
When B (beginning of block) or EOB (end of block) is detected, the counting of the backspace counter 22 is stopped. As a result, the backspace counter 22 counts the distance M'fi (or travel time) d from the noise detection position to the rear end of the front block.

(2) Even if the bank space counter 22 is stopped, the movement in the bank direction continues, and the control circuit 21 causes the comparison circuit 24 to compare the read data with the previous block value of the block register 23. In this case, each data block is assigned a block identification number (BID), so if the BID of the read data matches the value in the register 23, the control circuit 21 uses the match output from the comparison circuit 24 to identify the previous block. , and confirms that the aforementioned BOB is the end of the previous block. When the control circuit 21 detects EOB or BOB of the previous block from the read data, it stops the backward running. As a result, the head H1 is repositioned at the front end of the front block as shown in FIG. 3(B).

■ Next, the control circuit 21 runs the magnetic tape device 1 in the forward direction, checks the BID again from the read data of the head H1, and then detects the BOB (see Fig. 3 (C)).
position), a re-erase instruction is given to the erase circuit 20, and the count value of the bank space counter 22 is set in the erase circuit 20. As a result, the erase circuit 20 applies an erase signal to the magnetic tape device 1 for the time d counted by the backspace counter 22, and applies erase current to both heads HiH2. As a result, the area between the noise detection position and the end of the previous program is erased.

(2) During this re-erase, the control circuit 21 also monitors the read data and performs a noise check.If noise is detected, the process goes to step (2), and if no noise is detected, the process returns to step (2).

In this way, re-erase control is performed by the magnetic tape controller 2.
Further, the re-erase position is determined by detecting the previous block, and the erase area is determined by the measured value of the counter.

Although the present invention has been described above using one embodiment, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, there is provided an erase circuit for causing a magnetic head to erase the contents of a magnetic tape in response to an erase instruction, and an erase circuit that monitors read data from the magnetic head to control the running of the magnetic tape. and a control circuit for controlling the magnetic tape device, wherein the control circuit instructs the erase circuit to re-erase when noise is detected from the read data during the erase operation, the control circuit instructing the erase circuit to re-erase. A counter is provided to count the traveling distance or time of the magnetic tape in the bank direction, and upon detection of the noise, the control circuit moves the magnetic tape in the bank direction until the block identification number of the previous block on the magnetic tape is confirmed. After running, it is run in the forward direction for re-erasing, and the re-erase operation is performed based on the value counted by the counter, so firstly, the re-erase operation is performed without upper-level intervention. This has the effect of reducing the burden on higher-level personnel. Second, since the head reposition for re-erase is performed by checking the block identification number, it is possible to prevent destruction of data blocks due to repositioning errors due to bank spaces. Thirdly, since erasing is performed from the end of the previous data block by the count value of the counter, the portion that needs to be erased can be accurately erased, and the quality of re-erasing is also improved.

[Brief explanation of drawings]

Figure 1 is a block diagram of an embodiment of the present invention, Figure 2 is a time chart diagram of the configuration in Figure 1, Figure 3 is an explanatory diagram of the operation of the configuration in Figure 1, and Figure 4 is the processing flow of the configuration in Figure 1. FIG. 5 is an explanatory diagram of a conventional erase recovery method. In the figure, Hl, H2--magnetic head, MT--magnetic tape, 1-magnetic tape device, 2-magnetic tape control device,
20--Erase circuit, 21--Block read control circuit, 22--Backspace counter.

Claims (1)

[Claims] It has an erase circuit that causes a magnetic head to erase the contents of a magnetic tape in response to an erase instruction, and a control circuit that monitors read data from the magnetic head and controls the running of the magnetic tape. An erase recovery method for a magnetic tape device in which the control circuit instructs the erase circuit to re-erase when noise is detected from the read data, the distance or time that the magnetic tape travels in the backward direction at the time of re-erasing; A counter for counting is provided, and upon detecting the noise, the control circuit causes the magnetic tape to run in the backward direction until the block identification number of the previous block on the magnetic tape is confirmed, and then moves the magnetic tape in the forward direction for re-erasing. An erase recovery method for a magnetic tape device, characterized in that a magnetic tape device is run and a re-erase operation is performed based on a value counted by the counter.