JPH0561611A - Magnetic tape controller - Google Patents

Abstract

PURPOSE:To prevent the interruption of data transfer from a master device to a write buffer or from the write buffer to a magnetic tape device. CONSTITUTION:When data transfer from the master device 11 to the write buffer 16 is started by a write command, a timer 14 is started. A main control part 15 judges optimum timing by considering both of data volume to be transferred to the buffer 16 and transfer time counted up by the timer 14 and starts data transfer to the magnetic tape device 19. Thereby the buffer 16 can be prevented from being turned to an overflow state or an empty state. Consequently the interruption of each transfer can be reduced and data transfer can be efficiently executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape controller, and more particularly to a write buffer control system in the magnetic tape controller.

[0002]

2. Description of the Related Art Conventionally, in this type of magnetic tape controller, write data (hereinafter referred to as write data) from a host device is transferred to a write buffer during a write operation, and a fixed amount of data is stored in the write buffer. Then, the transfer of write data to the magnetic tape device is started, and the data is recorded on the magnetic tape.

[0003]

As described above, in the conventional magnetic tape controller, the transfer of write data from the host device to the write buffer and the transfer of write data from the write buffer to the magnetic tape device are asynchronous. Because there is
It has the following drawbacks.

First, when the transfer from the host device to the write buffer is faster than the transfer from the write buffer to the magnetic tape device, the write buffer is filled with data,
There is no choice but to interrupt or cancel the transfer from the host device.

The other is that when the transfer from the host device to the write buffer is slower than the transfer from the write buffer to the magnetic tape device, the write buffer becomes empty and the transfer to the magnetic tape device is interrupted or I have no choice but to cancel.

The object of the present invention is to monitor the amount and time of data transferred from the host device to the write buffer, and to determine the optimum time when it is determined that the write buffer will not be full or empty. By starting the transfer of write data from the buffer to the magnetic tape device, it is possible to eliminate the above-mentioned drawbacks, reduce the interruption of each transfer, and provide a magnetic tape control device capable of improving the efficiency of data transfer. Especially.

[0007]

SUMMARY OF THE INVENTION A magnetic tape controller according to the present invention comprises a write buffer for storing write data transferred from a host device and an overall operation of the write buffer and the magnetic tape device in response to a command from the host device. It has a main control unit for controlling, a detection unit for detecting the amount of data in the write buffer, and a timer for monitoring the data transfer time to the write buffer, and the transfer of the write data from the host device to the write buffer is started. When the timer starts, the main control unit determines the start time of the write data transfer based on the amount of data transferred by the write buffer detected by the detection unit and the transfer time measured by the timer. Transferring to the device.

[0008]

Embodiments of the present invention will now be described with reference to the drawings.

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

In FIG. 1, the magnetic tape controller 13 of the present embodiment has a write buffer 16 for storing the write data 12 transferred from the host device 11 and a write buffer and magnetic tape device 19 in response to a command from the host device. The main control section 15 for controlling the operation of the whole of the above, the detecting means 17 for detecting the amount of data in the write buffer, and the timer 14 for monitoring the data transfer time to the write buffer. Next, the overall operation of the magnetic tape controller of this embodiment during writing will be described. Since the write data 12 transferred from the higher-level device 11 and the write data 18 transferred to the magnetic tape device 19 are asynchronous, the write data 12 is once stored in the write buffer 16 and the main controller 15 writes it. When the write data is stored in the buffer 16 to some extent, the transfer to the magnetic tape device 19 is started. That is, the feature of the present invention is to consider the time when the above-mentioned main control unit 15 starts the transfer of the write data 18. FIG. 2 is a configuration diagram of the write buffer showing the time when the transfer of the write data according to the present embodiment is started. FIG. 2 shows, as an embodiment of the present invention, the write data amount in the write buffer and the timing of the transfer start. Transfer is started to the tape device, and "Write buffer is empty (EMPT
Y)), the transfer to the magnetic tape device is stopped. ”Conversely, when the transfer from the host device is fast, even if there is not much data in the write buffer, the magnetic tape The transfer is started to the device, and the state of “stopping the transfer from the host device because the write buffer is full (FULL)” is prevented. Will be described with reference to FIG.

FIG. 3 is a flowchart showing the processing of the control operation of the magnetic tape controller of this embodiment.

First, when the transfer from the host device to the write buffer is started (step 31), the timer is simultaneously started (step 32). While the write data from the higher-level device is being transferred to the write buffer, the main control unit monitors the amount of data transferred to the write buffer and the time from the start of transfer (step 33/34), and determines the appropriate time for the start of transfer. When it is determined that (step 35),
The transfer of write data to the magnetic tape device is started (step 36). This step (32 to 35) is the main part of the present invention. Here, regarding the judgment as to whether it is an appropriate time to start the transfer, this is to start the transfer if the data amount is large even if the transfer speed is slow, or to transfer even if the data amount is small if the transfer speed is fast. It means to start, and the following function can be considered, for example.

Transfer rate × data amount> constant value, but this is merely an example in which the above condition is expressed frankly, and the present invention includes the transfer rate or the transfer time in this judgment, which is shown here. The function itself is not specified. For reference, the following processing will be described. When the transfer from the write buffer to the magnetic tape device is started (step 3
6) If the amount of data in the write buffer is monitored and the write buffer becomes full (step 37), the transfer from the host device to the write buffer is stopped (step 310),
When the write buffer becomes empty (step 38), the transfer from the write buffer to the magnetic tape device is stopped (step 311). These monitoring operations are continued until the write data transfer is completed (step 39). When the steps (steps 32 to 35) are executed as described above, the full state or the empty state of the write buffer can be avoided as much as possible, and the control of suspending / resuming the data transfer becomes unnecessary.

[0014]

As described above, the magnetic tape continuation control device of the present invention monitors the amount and time of data transferred from the host device to the write buffer so that the write buffer does not become full or empty. By starting the transfer of write data from the write buffer to the magnetic tape device at the optimum time when it is determined that the interruption of each transfer can be reduced, the efficiency of data transfer can be improved. There is.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram of a write buffer showing the time when the transfer of write data according to the present embodiment is started.

FIG. 3 is a flowchart showing the processing of the control operation of the magnetic tape control device of the present embodiment.

[Explanation of symbols]

 11 Upper Device 12 Write Data 13 Magnetic Tape Control Device 14 Timer 15 Main Control Unit 16 Write Buffer 17 Data Amount Detection Means 18 Write Data 19 Magnetic Tape Device

Claims (1)

[Claims] 1. A write buffer for storing write data transferred from a higher-level device, a main control unit for controlling the overall operation of the write buffer and the magnetic tape device in response to a command from the higher-level device, and the inside of the write buffer. And a timer for monitoring the data transfer time to the write buffer, and starts the timer when the transfer of the write data from the host device to the write buffer is started. Then, the start time of the transfer of the write data is judged by the amount of data transferred by the write buffer detected by the detection means by the main control unit and the transfer time measured by the timer, and the write data is transferred to the magnetic field. A magnetic tape control device characterized by transferring to a tape device.