JPH0535509B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic tape control device that controls recording of data blocks having sequential block identification numbers (hereinafter referred to as block IDs).

Magnetic tape devices, which have long been used as external storage devices for information processing systems, are still widely used as data storage files and the like, taking advantage of their characteristics.

In particular, various measures have been taken to increase data transfer speed, increase density, and improve reliability and operability, but in order to achieve even more reliable data transfer, However, improvements in more detailed aspects are also required, and one of these is measures to improve the performance of write/read control for data blocks with sequential block IDs.

[Conventional technology]

FIG. 3 shows an example of the structure of a data block on a conventional magnetic tape.

Generally, the movement of the magnetic tape 1 cannot be started/stopped in an instant, so a buffer section g (this is called an interblock gap, or IBG) is used to provide a certain amount of time. It is necessary to provide an IBGg between data blocks, and as shown in FIG. 3A, an IBGg is provided between each data block #1 to #n.

When additionally writing a new data block on such magnetic tape 1, for example, as shown in FIG.
When erasing old data blocks #3 and #4 (indicated by dotted lines) and writing to new data block #3', the end of data block #2 is detected and the previous read mode is written. Switch to the mode and write.

At this time, a streamer that directly drives a tape reel with large inertia cannot be started/stopped within IBGg, so a repositioning operation is required.

That is, when the magnetic tape 1 is switched to the write mode as shown in FIG. 3, the constant running speed a is switched to a decelerated running speed b, and the tape stops at the SP point. It starts in the opposite direction from the SP point, moves the same distance as the stopping distance at a traveling speed c, then moves in the opposite direction again at a constant traveling speed, and when it recognizes data block #2, decelerates the stopping distance d and reaches the stopping point. Stop at RP.

Next, it restarts from the stopping point RP, accelerates in the normal direction, travels the same distance as the stopping distance, reaches the constant traveling speed f again at point P, and reaches the end of data block #2, which is the next lower number. When you recognize,
Data blocks #3 and #4 corresponding to the distance between the write head 2a and the erase head 2' are erased by the write head 2a to create an interblock gap.
After forming g', new data block #3' is written.

To control the running of a magnetic tape, a counter or the like is usually installed in a magnetic tape control device (not shown) to count the pulses output from a tachometer (not shown) attached to a tape reel motor, etc. The moving distance and stopping position are controlled by the counted value.

[Problem that the invention seeks to solve]

Additional writing to new data block #3' is performed using the above operation, but the restart position RP
The point P at which the vehicle accelerates in the normal direction and reaches a constant travel speed f must be almost the end position of the actual data block #2, but depending on the control situation, it may be at the end position of the data block #3. In this case, there is a possibility that all data in data block #3 may not be erased.

In addition, since data is erased only by the write head 2a, it is possible to erase only the corresponding track width, so there is a problem that unerased data may remain when off-track occurs.

[Means for solving problems]

The present invention realizes a novel magnetic tape control device that solves the above-mentioned problems. When erasing an old data block and additionally writing a new data block after the old data block, the block detecting means detects a data block one number smaller than the old data block to be erased, and A dummy block is formed by overwriting the dummy block generated by the dummy block generating means on the data block to be erased after the data block with the lowest number, and then the new data block is additionally written. and control means for causing the dummy block detecting means to skip that part in response to the detection of the dummy block and read the next data block when reading. Solved by tape controller.

[Effect]

When writing an additional data block to the target position, detect a data block one number smaller than the target position, use the write head to overwrite the dummy block on the data block from the end of that block, and then write the new data block. Perform additional writing. Therefore, no data block remains unerased.

When reading, when the dummy block is detected,
Skip it as unmanaged and read the new data block immediately.

〔Example〕

Figure 3A shows read head 2b and write head 2.
The positional relationship between the read/write head 2 including a and the erase head 2' is shown.

According to the present invention, when writing a data block, the write head 2a writes data blocks subsequent to the end of data block #2, which is one number smaller than the data block at the target position, that is, data blocks #3 and #4 in this example. Write dummy data to form a dummy block. After removing the interblock gap g' from data block #2, additional writing of new data block #3' is performed.

FIG. 1A is a block diagram showing an embodiment of the magnetic tape control device according to the present invention, FIG. 1B is a flowchart of the magnetic tape control device according to the present invention, and FIG. 2 is a magnetic tape control device according to the present invention. In the control status diagram of the device, A shows the writing time and B shows the reading time.

Next, the operation of this embodiment will be explained with reference to FIGS. 1A and 1B.

(ST-1); Based on the information transferred from the host device (not shown), the magnetic tape control device 3 determines that it is write control, and writes the write data from the host device (not shown). is outputted to the write formatter 7, and the write formatter 7 outputs it to the magnetic tape device 4 together with data regarding the data block format.

(ST-2); Information indicating that additional write control is required from the magnetic tape device 4 is sent to the block control circuit 5.
is received.

(ST-3); Under the control of the block control circuit 5,
The magnetic tape device 4 performs backspace from the target position to data block N-1 which is one number smaller, skips data block N-1 in the opposite direction, and stops at the restart point.

(ST-4); Next, perform a space operation for data block N-1.

(ST-5); When the block ID of data block N-1 and its end are confirmed during space operation, the read mode is switched to write mode, and a dummy block is output from the dummy block generation circuit 6 to the magnetic tape device 4. Data is written to the dummy block by the write head 2a.
Form a DUM.

(ST-6); After the magnetic tape control device 3 finishes writing the dummy block data of a predetermined length,
Additional writing of the target data block N is controlled, and when the writing is completed, all controls are ended.

(ST-7); If the instruction from the host device (not shown) is not a write operation, it is determined whether or not it is a read operation, and if it is a read operation of data blocks N-1 and N, the magnetic tape device Data block N-1 is read first.

(ST-8); The dummy block detection circuit 9 detects a dummy block in the next data read.

(ST-9); The magnetic tape control device 3 controls the magnetic tape control device 4 to skip a dummy block, and after skipping the dummy block, reads the next data block N and performs the read operation. Terminate it.

〔Effect of the invention〕

As described above, by forming a dummy block according to the present invention, problems such as data left unerased due to incomplete erasure caused by off-track or unstable positioning can be solved, and additional writing of data blocks and additionally written data can be avoided. This has the effect that block reading can be efficiently controlled.

[Brief explanation of the drawing]

FIG. 1A is a block diagram showing an embodiment of the magnetic tape control device according to the present invention, FIG. 1B is a flowchart of the magnetic tape control device according to the present invention, and FIG. 2 is a magnetic tape control device according to the present invention. In the control status diagram of the apparatus, A shows the writing time, B shows the reading time, and FIG. 3 shows an example of the configuration of data blocks on the magnetic tape. In the figure, 1 is a magnetic tape, 2 is a magnetic head, 3 is a magnetic tape controller, 4 is a magnetic tape device, 5 is a block control circuit, 6 is a dummy block generation circuit, 7 is a write formatter, and 8 is a read formatter. ,
9 indicates a dummy block detection circuit.

Claims (1)

[Scope of Claims] 1. A magnetic tape control device for controlling recording of a data format comprising data blocks having sequential block recognition numbers and gaps of a predetermined length between the data blocks, the magnetic tape control device comprising: a dummy block; A dummy block detection means 9 detects the written dummy block. When erasing an old data block and additionally writing a new data block after the old data block, A data block one number smaller than the old data block to be erased is detected, and a dummy block generated by the dummy block generation means is placed on the data block to be erased after the data block one smaller number. A dummy block is formed by overwriting the dummy block, and then the new data block is additionally written.When reading, when the dummy block detecting means detects the dummy block, that part is skipped and the next data block is written. A magnetic tape control device comprising: control means 5 for reading data blocks.