JPH0150991B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention is directed to a magnetic tape control device that uses labels and tapes that are likely to cause block skipping.
The present invention relates to a write control circuit that improves the reliability of data reading by increasing the gap (IBG) before or after a block with a short write length.

(2) Background of the Technology In conventional magnetic tape devices, the format in which information is written on the magnetic tape, that is, the tape format, has been standardized to a certain extent.
For example, in the standard label format shown in Figure 1, the first block from the tape start marker BOT is the volume label VOL1,
The next two blocks are header label HDR1,
It is HDR2. Additionally, two blocks of trailer labels EOF1 and EOF2 are placed following the tape mark after the data block. The size of these label blocks is 80
Specified in byte length. Furthermore, EOT is
This is an end-of-tape marker.

By the way, each block is separated by an IBG, and when the magnetic tape stops running, the head detects the end of the block, decelerates the tape, and then stops the magnetic tape. is IBG
Stop at a certain position within. The tape starts running from the stop position.

Therefore, when reading a tape, for example, the distance for the read head to reach the beginning position of the next block from its stop position is relatively short.
If the next block is a block with a short write length like the label block described above, that block will be read while remaining in the unstable running state at the start of tape running. Therefore, if vibration or slippage occurs in the tape, the read head may skip over blocks, which poses a problem.

(3) Object and structure of the invention In order to solve the above-mentioned problems, the present invention, when writing a short block on a tape format where there is a possibility of skipping, writes the IBG before and after the block. The length is set to be sufficient to allow the tape to reach a stable running state.

The present invention provides, as a configuration for this purpose, a magnetic tape control device including means for detecting a write command, and in response to the write command detecting means, a short block length predicted to be written based on the magnetic tape format. means for setting the number of blocks, means for storing the set number of blocks, means for increasing the inter-block gap when writing of the blocks is executed, and means for setting the number of blocks when writing of the blocks is executed. It is characterized by comprising means for increasing or decreasing the contents of the storage means by a fixed number, and means for activating the inter-block gap expansion means when the contents of the block number storage means are not a predetermined number. do.

(4) Examples of the invention Examples of the invention will be described below.

FIG. 3 is a schematic configuration diagram of an embodiment of the present invention.
In the figure, 1 is a magnetic tape device, 2 is a count value storage circuit for the number of block write times with a short block length, 3 to 5 are magnetic tape control devices that control the magnetic tape device 1 in parallel, and 6 to 8 are blocks with a short block length. This is a block number counter that counts the number of times a block is written.

The block number counters 6 to 8 are preset with the number of related blocks for which it is necessary to expand the preceding and succeeding IBGs when writing from the tape start end marker BOT or when writing a tape mark. When writing to one block (block write) is successful, it is counted down by 1.

The count value storage circuit 2 is connected to the magnetic tape device 1.
However, as shown in the figure, multiple magnetic tape control devices 3
To maintain continuity of control by notifying the current block number count value to any magnetic tape control device that has started the control operation when the magnetic tape is controlled in parallel by any one of 5 to 5. It is necessary for

In operation, for example, in the case of a tape format as shown in Figure 1, when writing is started from BOT, the total length of three blocks (volume label and header label) is short, so writing is not possible. The value 3 is preset in the block number counter of one magnetic tape controller executing the instruction. Next, when writing a block, unless the counter value is 0, the start of block writing is delayed and erased by a predetermined distance, and then block writing is performed. As a result, the IBG becomes longer.

When the block write is completed correctly, unless the counter value is 0, it is counted down by 1. When the block write is not performed correctly and when the value of the counter is 0, the counter does not count down.

As another example method to lengthen the IBG, BOT
After processing or writing blocks such as tape marks and EOF, erase is executed without stopping the tape immediately, and if the tape is stopped after traveling a predetermined distance, the BOT can
Alternatively, the IBG can be made longer by a predetermined number of blocks from tape marks or other blocks. According to this method, after writing a short block, it is possible to ensure a sufficient distance from the end of the block to the read head, so that the block can be recognized correctly when returning from the stopped position in the backward direction. becomes possible.

Furthermore, as another embodiment, it is also possible to simultaneously combine the method of delaying the start of writing described above and the method of delaying the stop of the tape after the end of writing.

FIG. 4 is a detailed configuration diagram of an apparatus according to an embodiment of the present invention. In the figure, 9 is a host device such as a CPU, and 10 is a host device such as a CPU.
is a magnetic tape control device, 11 is a magnetic tape device,
12 is a magnetic tape, 13 is an instruction decoding circuit, 14 is
AND circuit, 15 is a preset value determination circuit, 16
is a write/tape mark instruction execution control circuit, 17
is a write/data block instruction execution control circuit, 1
8 is an OR circuit, 19 is a block number counter, 20
is the IBG length control circuit, 21 is the BOT detection mechanism, 22
is a count value storage circuit, 23 is a writing mechanism, 2
4 is a BOT marker.

The write-related commands given from the host device 9 to the magnetic tape control device 10 include three commands: an erase command, a write data block command, and a write tape mark command.

The instruction decoding circuit 13 decodes the instruction given from the host device, and if it is a write type instruction,
When "1" is given to one input of the AND circuit 14, and if it is a write/tape mark command, the preset value determination circuit 15 and the write/tape mark command execution control circuit 16 are activated; If it is a block instruction, the write/data block instruction execution control circuit 17 is activated.

When a write command is given and the BOT marker 24 is detected by the BOT detection mechanism 21,
The BOT signal is applied to the other input of AND circuit 14. Therefore, the AND circuit 14 outputs "1" and activates the preset value determining circuit 15.

The preset value determining circuit 15 determines the preset value by a preset signal via the OR circuit 18 when a write system command is given and a BOT marker is detected, or when a write/tape mark command is given and the writing is successful. The obtained block number is preset in the block number counter 19.

If the given write-related command is a write data block command, the write command execution control circuit 17 first controls the execution of data block writing of the volume label. counter 19
The preset values within are temporarily stored in the count value storage circuit 22.

The IBG length control circuit 20 includes a count value storage circuit 2
2, and unless it is "0", the write mechanism 23 delays the timing of starting data block writing as described above, or delays the tape running stop after the writing is completed, and executes erase. Control operations such as

When the volume label is successfully written, the write/data block instruction execution control circuit 17
The data block write success signal is detected by the counter 19.
and counts down the contents of the counter by 1. The result is "2", and the contents of the count value storage circuit 22 are updated with this value.

The write data block command for writing the next two header labels is executed in the same way, and finally the contents of the counter 19 become "0". Therefore, since the contents of the count value storage circuit are also updated to "0", the IBG length control circuit 20 does not operate for subsequent data block writing, and no IBG expansion processing is performed.

Next, when a write tape mark command is given, the counter 19 is preset to "2".
As a result, the IBG length control circuit 20 is activated again and performs IBG expansion processing when writing block data for the two trailer labels following the tape mark. Every time the data is written correctly,
The contents of counter 19 are counted down to "0"
When the length of the IBG is reached, the IBG length control circuit 20 stops the IBG expansion process.

The preset values preset in the preset value determination circuit 15 may be selected and changed as appropriate according to the label configuration of the magnetic tape volume to be used. In any case, since the number of IBGs expanded by the present invention is small, the effect on the reduction in the utilization efficiency of the magnetic tape is almost negligible.

(5) Effects of the Invention As described above, according to the present invention, IBGs of sufficient length are set before and after short blocks that are likely to be skipped, so blocks can always be read in a stable state. It becomes possible to read.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a standard label format tape format, Fig. 2 is an explanatory diagram of the head position when the tape is stopped and started, Fig. 3 is a schematic configuration diagram of an embodiment of the present invention, and Fig. 4 is an embodiment of the present invention. FIG. 3 is a detailed configuration diagram of an example. In the figure, 10 is a magnetic tape control device, 11 is a magnetic tape device, 12 is a magnetic tape, 13 is an instruction decoding circuit, 15 is a preset value determining circuit, 17 is a write/data block instruction execution control circuit, and 19 is a block number counter. , 20 is an IBG length control circuit, 21
is a BOT detection mechanism, 22 is a count value storage circuit,
23 indicates a writing mechanism.

Claims (1)

[Claims] 1. In a magnetic tape control device, means for detecting a write command, and means for setting the number of short block length blocks expected to be written based on the magnetic tape format in response to the write command detecting means. means for storing the set number of blocks; means for expanding the inter-block gap when writing the blocks; and storing the contents of the block number storage means to a certain number when writing the blocks. 1. A magnetic tape write control circuit comprising: means for increasing or decreasing the number of blocks; and means for activating the inter-block gap expansion means when the content of the block number storage means is not a predetermined number.