JPS6059432A - Data buffer control method of input and output device - Google Patents

Abstract

PURPOSE:To prevent other input/output devices from being kept waiting for a long period of time by giving a request to a host device for transfer of a new data block in case the remaining capacity value of a data buffer is larger than the value of the data block which is stored last. CONSTITUTION:When the transfer of a data block (b) is through to a streaming magnetic tape part for the writing purpose. Then the information on the data input and output counters 3 and 4 are delivered to a block length counting circuit 8 via a subtractor circuit 6. While a data buffer part 1 delivers the information on a block (c) which is stored last in the part 1 to a block length counting circuit 7. A comparator 9 performs comparison and counting to decide whether the idle capacity length of the part 1 is larger than the block length of the (c). Then the comparator 9 delivers a signal to a data transfer control part, and a block (d) is transferred from a host device during the writing of the block (b).

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical field of the invention The present invention requests data in blocks of data required by an input/output device from a host device in advance, stores it in a data buffer, and stores it sequentially. The present invention relates to a data buffer control method for an input/output device that transfers data in units of data blocks to the input/output device.

(b) Technical Background As the use of information processing devices has become more sophisticated and complex, there has been a demand for the development of magnetic tape devices that can be used for various purposes. One example is a streaming magnetic tape device that uses a low-cost motor with long inertia when starting and stopping as a tape drive motor.

When writing information with this streaming magnetic tape device, data for multiple data blocks is stored in a data buffer in order to prepare for writing the information within a predetermined data block interval (IBG) range.

It is necessary to take measures such as correcting the difference in transfer speed.

It is desired to realize various data processing methods that can process data at normal processing speeds by taking advantage of the characteristics of the streaming magnetic tape device and data buffer described above.

(c) Prior Art and Problems A conventional data buffer control method will be explained using a streaming magnetic tape device as an example with reference to the drawings.

FIG. 1 is a block diagram of a conventional data buffer.

FIG. 2 shows an example of data recording by a streaming magnetic tape device.

In the figure, 1 is a data buffer section, 2 is a streaming magnetic tape section, 3 is a data buffer input counter, and 4 is a data buffer input counter.
is the data buffer output counter.

5 each indicate a magnetic tape.

Note that a - d are data blocks i - iv, a' to C
' is the data block interval (hereinafter abbreviated as ■BC).

e is the motion locus of the magnetic tape 5, r is the stop position of the magnetic tape 5, and the rising edge point 1g in the reverse running direction is also the stopping position of the magnetic tape 5, and the rising point in the forward running direction, h. indicate the speed of the magnetic tape 5, respectively. Further, the lengths of data blocks (1 to 1v) a to d are variable length format.

The data buffer unit 1 is a multi-block buffer that can store multiple data blocks. Data in units of C blocks is previously transferred from a host device (not shown), stored, and processed by the streaming magnetic tape unit 2. At the same time, the block star 1 address and block length are recorded in the management table in the data buffer section 1. The data buffer input counter 3 stores a data block (i to
1v) Count a-d, data buffer output counter 4
is the data buffer section 1 in the streaming magnetic tape section 2.
Count the data blocks (i-iv) ad to be transferred from.

Example of data recording that should now be stored after data block (ii) b is written to the magnetic tape 5') (ii
i) If the transfer from the host device (not shown) of c is slow for some reason and writing preparations cannot be made between IBGb' of data block (ii) b and data block (iii) c, the magnetic The motion trajectory e of the tape 5 turns around at one point and is positioned at the starting position of point g.
When the transfer of data block (iii)C is completed and it is stored in the data buffer section I, the streaming magnetic tape a1;2 rises from point g and starts writing again to write data block (iii)c. data block (
iii) While writing c, data block (iv) d and subsequent blocks are prefetched and stored in data buffer 1.

Also, when an error occurs when writing any of the data blocks (i to 1v) a to d and you try again, the process automatically returns to the point before the target data block (i = iv) a''-d and tries again. I do.

If the storage capacity of the data buffer unit 1 becomes full during transfer to the data buffer unit 1, the host device (not shown), the data transfer continues. Furthermore, if an error occurs in the current write, the operation trajectory e, f, 'g is repeated and the error retry is executed, which reduces the data transfer time to the data buffer section 1 of the host device (not shown). Furthermore, there is a problem that the service to other input/output devices (not shown) connected to the same host device (not shown) may be interrupted for a long time.

(d) Purpose of the Invention The purpose of the present invention is to provide a novel data buffer control method for an input/output device that eliminates the above-mentioned drawbacks. In particular, the data block length controlled by individual software is often a fixed length. Focusing on this, it is equipped with a counter that counts the length of the data block, and each time the transfer of the data block input to the data buffer is completed, the contents of the counter are updated to the latest data block length, and the remaining capacity of the data buffer is calculated. When the value is greater than the last stored data block length counter value, the host device is requested to transfer a new data block, and other input/output devices connected to the same host device are requested to transfer a new data block during the data block transfer. The object of the present invention is to realize a data buffer control method for a hand-cutting machine that quickly transfers data blocks so that the machine does not have to wait for a long time.

(e) Configuration of the Invention The present invention is applicable when data in units of predetermined data blocks is transferred from a host device to an input/output device.

Data in units of data blocks required by the input/output device is requested from the host device in advance and stored in a data buffer provided to compensate for differences in data transfer speeds, and then A data buffer control method for an input/output device in which stored data in units of data blocks is transferred to the input/output device, the data buffer having an empty area larger than the length of the data block last stored in the data buffer. This can be achieved by a data buffer control method for an input/output device, which is characterized in that when it is known, a secondary transfer request for the data block is made to the host device, and the data block is quickly transferred.

4f) Examples of the invention The present invention will be explained below with reference to the drawings.

FIG. 3 shows an embodiment of the streaming magnetic tape device according to the present invention.

In the figure, 6 represents a subtraction circuit, 7 and 8 represent data block length counting circuits, and 9 represents a comparison circuit.

In this embodiment, data buffer input counter 3. 4. A data processor to be transferred to the streaming magnetic tape unit 2; A subtraction circuit 6 which takes the difference between the output of the data buffer input counter 3Φ and the output of the data buffer output counter 4 and outputs it to the data block length counting circuit 7. 7. Data block length 41 count circuit that receives the latest data block information from the data buffer 1 part 1 from the management table in the data buff 1 part 1, counts the last stored data block length, and outputs it to the comparison circuit 9. A data block length counting circuit 8 for counting the free capacity length in the data buffer section 1 based on the information from the subtraction circuit 6. A comparison circuit that compares the output information of the data block length counting circuit 7 and the data block length counting circuit 8 and outputs a signal only when the output of the data block length counting circuit 8 is equal to or larger than the output of the data block length counting circuit 7. It consists of 9.

Next, the operation of this embodiment will be explained with reference to FIGS. 1 to 3.

Current data block (ii) b and data block (ii)
i) c is stored in the data buffer section 1;

When the data block (ii) b has been transferred to the streaming magnetic tape unit 2 for writing, the information from the data buffer input counter 3 and data buffer output counter 4 is output to the data block length counting circuit 8 via the subtraction circuit 6. do. On the other hand, from the management table in the data buffer section l, the data block (i
ii) The information of c is output to the data block length counting circuit 7.

The data block length counting circuit 7 counts the data block length of the data block (1ii) C based on the information of the input data block (iii) c and outputs it to the comparison circuit 9. Based on the obtained information, the free capacity length of the datum node section 1 is calculated by the number δ1, and the comparator circuit 9
Output to. Comparison episode [28! Compare and count whether the free capacity length of data buffer section 1 is greater than or equal to the data block length of data block IZI7 (iii) c,
A signal is output to a data transfer control section (not shown) to have data block (iv) d transferred from a host device (not shown) while data block (ii) b is being written.

If the data blocks are transferred from the 0-position device (not shown) under the above conditions, generally the length of each data block will not be different, so it will be the same as before. In addition, since the data buffer 1 is full during the transfer, other input/output devices (not shown) connected to the same host device (not shown) are not kept waiting.

(g) Effects of the invention As described above, the counter is provided with a counter that counts the length of the data block by 81, and the contents of the counter are updated to the latest data block length every 1J4 when the transfer of the data block input to the data buffer is completed. When the remaining capacity value of the data-rich buffer is larger than the counter value of the last data block stored in the data buffer, a request is made to the higher-level device to transfer a new data block. The present invention has the advantage that it is possible to provide a data buffer control method for an input/output device that quickly transfers data blocks so as not to cause other input/output devices connected to a host device to be delayed for a long time.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional data buffer. FIG. 2 shows an example of data recording in a streaming magnetic tape device, and FIG. 3 shows an embodiment of the streaming magnetic tape device according to the present invention. In the figure -ζ, ■ is the data buffer section, 2 is the streaming magnetic tape section, 3 is the data buffer input counter,
4 is the data buffer 1 output counter. 5 is a magnetic tape, 6 is a subtraction circuit, 7.8 is a data block length counting circuit, and 9 is a comparison circuit.

Claims (1)

[Claims] When data in units of predetermined data blocks is transferred from a host device to an input/output device, the data required by the input/output device is stored in a data buffer provided to compensate for the difference in data transfer speed. A data buffer control method for an input/output device in which data in block units is requested and stored in advance from the host device, and the stored data in block units is sequentially transferred to the input/output device. The input/output device is characterized in that when an empty space longer than the length of the data block last stored in the data buffer is found, a primary transfer request for the data block is made to the host device. Data buffer control method.