JPH054693B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] This control device is equipped with a data buffer that stores data for several blocks of a reel-to-reel driven magnetic tape. A control method is shown in which the required data transfer processing is performed without driving the magnetic tape.

[Industrial application field]

The present invention relates to a magnetic tape control device, and more particularly to a magnetic tape control method for rationally shortening response processing time to a group of single commands issued from a host device.

[Conventional technology]

Since such a magnetic tape control device operates the magnetic tape device in response to commands from a host device, if a mixture of forward and backward commands is issued, the tape is moved forward or backward accordingly. Therefore, unlike a streaming magnetic tape device, the access time is long and the tape may overrun depending on the start-stop characteristics. As a result, the tape cannot be stopped within a predetermined IBG (Inter Block Gap) and a tape repositioning operation is performed, reducing the time efficiency of program processing.

In order to improve this, a data buffer may be provided in the magnetic tape control device, and data may be sequentially input from the host device in advance during data writing, and the input data may be transferred to the magnetic tape device via the buffer. Alternatively, when reading data, necessary data is written into a buffer in advance and then sent to the host device at high speed.

The present invention is particularly intended to improve the efficiency of data processing when the same command sequence is used to process the minimum information related to file opening of magnetic tapes employing various file formats. It is something.

[Problem that the invention seeks to solve]

FIG. 4 shows an example of the arrangement of program processing blocks related to opening a certain file.

Following BOT, a volume label block 31 (Vo1), a plurality of header blocks 32 (HD1) to 34 (HD3), and a tape mark block 35 (FM) are sequentially written on the magnetic tape 30.

When opening a magnetic tape recorded according to such a fixed format using the following command sequence, it is necessary to access the same block position several times.

Read command (Vo1) → Read command (HD1) →
Backspace command (HD1) → Backspace command (Vo1) → Read command (Vo1) → Write command (new HD1) In other words, when a single read or write command is issued from the host device, the same block position is read several times. Since data is often accessed repeatedly, it is essential to improve the efficiency of data processing.

[Means for Solving the Problems] An object of the present invention is to effectively use the data inside the data buffer obtained by prefetching, so that the magnetic tape can be read from the controller in response to commands such as read commands from the host device. The objective is to independently determine the necessity of sending commands to devices and shorten the time required to process commands from a controller to a host device.

To achieve this purpose, in a magnetic tape control device that is equipped with a data buffer that stores data for multiple blocks and is equipped with a block read-ahead control function, a logical block that indicates the block position corresponding to a command from the host device 19 at a certain point in time is used. A pointer register 1, a physical block pointer register 3 in which the magnetic tape is positioned at the time, a buffer avalid forward counter 6 and a buffer avalid back word counter 7 indicating the validity of the data buffer 12 are provided; According to the values 6 and 7, the host device 1
When a magnetic tape control backspace block or pace block instruction 21 or a burst transfer instruction such as a read or read backword instruction 20 is received from 9, the value of the logical block pointer register 1 is changed to drive the magnetic tape device 18. This magnetic tape control method is characterized in that the completion of a control command is notified without the need for a control command to be completed.

[Effect]

The prefetch data stored in the buffer 12 of the control device 16 is effectively used, and when a read or read back word command 20 is issued from the host device, the data in the buffer 12 is transferred to the host device or the block pointer of the buffer is used. By moving the , command completion is reported to the host device without actually driving the magnetic tape device.

A buffer valid counter 5 is a buffer valid counter 6 which indicates the number of blocks that do not need to be actually operated in the forward direction command.
(VFC) and a buffer reverse word counter 7 (VBC) which indicates the number of blocks that do not need to be actually operated in response to a backward direction command.
And when the value of the counter 6 or 7 is zero,
Make the user realize that the magnetic tape must actually be moved.

〔Example〕

FIG. 1 is a system block diagram of an embodiment of magnetic tape control according to the present invention.

FIG. 2 is a state diagram for storing data in four divisions in the buffer, and FIG. 3 is a diagram showing the arrangement of pointer control bits of a pointer register and a counter.

In the system block diagram, a logical block pointer (BP) register 1 in the control device 16 indicates the bit corresponding to the buffer address of the block to be sent next by the control device to the host device 19 as “1”. The physical block pointer (HP) register 3 is a shift register that indicates the number of bits corresponding to the address to be sent next by the control device to the buffer 12 as "1", and indicates the number of bits for dividing the buffer. Define the direction as left shift.

Each time the control device 16 reads a single block of data from the magnetic tape device 18 and writes it to the buffer 12, it shifts "1" in the HP register 3 to the right and transfers a single block of data to the host device 19. Shift “1” in BP register 1 to the right.

When the bit positions of HP register 3 and BP register 1 match, it indicates that the data transferred to the host device 19 has not yet been taken into the buffer 12, and the data transferred to the host device 19 is transferred to the host device until the HP register 3 is shifted to the right by one bit or more. Make data transfer to wait.

In this embodiment, a tape control block such as BOT (Biginnig Of Tape) or
When an EOT (End Of Tape), end of data block, or tape mark block is detected, the preread operation is stopped.

Figure 3 shows the HP register, BP register, and
7 is a diagram showing the states in which the pointer control bits in the VFC counter 6 and the VBC counter 7 are shifted. FIG.

In the figure, A is the initial state and B is the header block 32.
(HD1), the data of the magnetic tape device 18 has been written to the buffer, and the volume label block 31 (Vo1) has been transferred to the host device 12.
When receiving a backspace command from 2,
Each figure shows a state in which the BP register is shifted to the left and the magnetic tape device is not driven.

〔Effect of the invention〕

As explained above, according to the magnetic tape control method of the present invention, as long as valid prefetch data exists, it is possible to respond to forward and backward commands from the host device without driving the magnetic tape device. Therefore, command response time can be significantly shortened.

[Brief explanation of the drawing]

FIG. 1 is a system block diagram of a tape control embodiment of the present invention, and FIG. 2 shows a buffer divided into four parts. FIG. 3 is a layout diagram of the control bits of the pointer register and counter, and FIG. 4 is a layout diagram of routine blocks related to file opening. In the figure, 1 is the logical block pointer register, 3
1 is a physical block pointer register, 6 and 7 are buffer abutment counters, 16 is a magnetic tape control device according to the present invention, 18 is a magnetic tape device, 19 is a host device, 20 is a read or read back word instruction, and 21 is a space block instruction or a backspace block instruction.

Claims (1)

[Scope of Claims] 1. In a magnetic tape control device equipped with a data buffer for accumulating data for a plurality of blocks and equipped with a block prefetch control function, a logical block pointer indicating a block position corresponding to a command from a host device 19 at a certain point in time. A register 1, a physical block pointer register 3 in which the magnetic tape is positioned at the time, a buffer valid backward counter 6 indicating the validity of the data buffer 12, and a buffer valid backward counter 7 are provided; , 7, the host device 1
When a magnetic tape control backspace block or pace block instruction 21 or a burst transfer instruction such as a read or read backword instruction 20 is received from 9, the value of the logical block pointer register 1 is changed to drive the magnetic tape device 18. A magnetic tape control method characterized in that the completion of a control command is notified without the need for a control command to be completed. 2. When receiving the burst transfer command, refer to the values of the buffer avalid forward counter 6 and the buffer avalid back word counter 7, and if the data in the buffer 12 is valid, the logical block pointer register is 1 to the buffer 12 without reading data from the tape.
Claim 1 is characterized in that it notifies that the instruction has been completed by transferring data within the scope of the invention.
Magnetic tape control method described in Section 1.