JP2953874B2 - Magnetic tape device control method for input / output channel device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a magnetic tape device of an input / output channel device in a computer system, and more particularly, to a beginning of a magnetic tape, that is, a BOT (Beginning of).
The present invention relates to a magnetic tape device control method suitable for writing data from a tape.

[0002]

2. Description of the Related Art Generally, SCSI (Small Computer System Interface) is used as an input / output channel device of a computer system.
3) Various external storage devices such as a magnetic disk device, an optical disk device, and an 8 mm tape device can be connected via one input / output bus represented by a bus.

In such a system in which various external storage devices can be connected to one input / output bus, there is an advantage that the number of input / output channel devices can be minimized. On the other hand, there is a gap such as a gap in performance specifications between the external storage devices, and input / output control of the input / output channel device is difficult to absorb.

For example, in the case of an 8 mm tape device, it takes about 40 seconds to write data from a BOT to a tape, during which time the input / output bus is occupied, and another high-speed accessible external storage device such as a magnetic disk device is used. (Random access device) performance is significantly reduced.

[0005]

As described above, in a computer system in which various external storage devices are connected to one input / output channel device via one input / output bus,
For example, it takes about 40 seconds to write data from a BOT to a tape of an 8 mm tape device. It takes about 40 seconds for the writing operation of the 8 mm tape device itself, which is inevitable due to the mechanism of the device.

Conventionally, however, the input / output bus is occupied by the tape device during the write operation of the tape device. Therefore, a high-speed accessible external storage device such as a magnetic disk device and the input / output channel device are not connected. Since input / output control cannot be performed, there is a problem that the performance of these external storage devices that can be accessed at high speed is reduced, and the performance of the entire system is reduced.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an input / output channel device which is provided on a tape of a magnetic tape device represented by an 8 mm tape device.
When writing data from T), it is possible to prevent the input / output bus to which various external storage devices including the magnetic tape device are connected from being occupied by the magnetic tape device for a long time,
It is an object of the present invention to provide a method of controlling a magnetic tape device of an input / output channel device which can improve the performance of the entire system.

[0008]

SUMMARY OF THE INVENTION According to the present invention, when an I / O channel device writes data from a BOT to a tape of a magnetic tape device represented by an 8 mm tape device, an I / O bus is connected to the I / O channel device. After the amount of data transferred through the data buffer and stored in the data buffer of the magnetic tape device reaches the reference amount, writing to the magnetic tape is performed after a long time (approximately 40 seconds in the case of an 8 mm tape device) necessary for the mechanism. so, for during this period can not be transferred to the magnetic tape device subsequent data from the input-output channel unit, the input-output bus Noting that would be occupied long term by the magnetic tape device, the tape BOT tape drive Day of
Data write, the transfer amount during the first write data transfer increases.
At least one write data without exceeding the reference amount
Data transfer to the magnetic tape unit.
When writing data while the disk is positioned at the BOT of the tape, the data is to be written from the BOT.
The amount of write data that does not exceed the reference amount, by transferring from the input-output channel unit outputs a write command to the tape device, a first step of storing the data in the data buffer of the tape unit, A write file mark command for instructing writing to a magnetic tape by attaching n file marks to the data stored in the data buffer and issuing a write file mark command to the file mark number designated value n (count n) By outputting the value as “0” to the magnetic tape device, the data stored in the data buffer of the magnetic tape device by the execution of the first step is forcibly added to the BOT of the magnetic tape without adding a file mark. And a second step of writing from the beginning.

[0009]

In the above configuration, when writing data from a BOT to a tape of a magnetic tape device, first, a write command is output from the input / output channel device to the tape device, and the write target from the BOT is written. Reference amount
The write data of the amount not exceeding is transferred (first step). Then, the write data is stored in the data buffer of the magnetic tape device, and the operation of the write command is completed.

Next, a write file mark command in which the value of the count n is "0" is output from the input / output channel device to the magnetic tape device (second step). Then, even if the amount of write data stored in the data buffer of the magnetic tape device has not reached the reference amount, the write data is taken out and written from the BOT of the magnetic tape. At this time, since the value of the count n of the write file mark command is “0”, no file mark is added.

That is, according to the above configuration, by executing the dummy write file mark command, the write data stored in the data buffer by the preceding write command can be written even if the amount does not reach the reference amount. Data can be immediately written from the BOT of the magnetic tape. Assuming that the magnetic tape device is, for example, an 8 mm tape device, this writing operation itself takes about 40 seconds as in the conventional case, but during this time, the input / output bus is not occupied by the magnetic tape device.

[0012]

1 is a flowchart showing a method for controlling an 8 mm tape device of an input / output channel device according to an embodiment of the present invention. FIG. 2 is an input / output channel to which the 8 mm tape device control method shown in the flowchart of FIG. 1 is applied. FIG. 1 is a system configuration diagram of a computer system including a device.

In FIG. 2, reference numeral 1 denotes a CPU (central processing unit) serving as a control center of the system, and 2 denotes a main storage device used for storing various programs and data. The CPU 1 and the main storage device 2 are connected to a system bus 3.

A channel device (hereinafter, referred to as a channel device) is connected to the system bus 3.
4) are connected. The channel 4 is connected to the main storage device 2 and a magneto-optical disk device 6 to be described later independently of the CPU 1 in accordance with an instruction from the CPU 1.
9. Controls data input / output with external storage devices such as the CD-ROM device 10 and the 8 mm tape device 20.

The channel 4 is connected to various external storage devices via one input / output bus 5 typified by a SCSI bus.
For example, magneto-optical disk devices 6 to 9, CD-ROM device 1
0 and 8 mm tape devices 20 are connected. The 8 mm tape device 20 has, for example, a 128 KB (kilobyte) data buffer 21 for temporarily storing write data transferred in response to a write command output from the channel 4.

Data buffer 21 of 8 mm tape device 20
The reference amount for writing data from to the tape can be set arbitrarily. In this embodiment, it is assumed that the reference amount is set to 128 KB. That is, in this embodiment, when 128 KB of data is stored in the data buffer 21, the data buffer 2
It is assumed that writing from 1 to the tape is performed.

The 8 mm tape device 20 adds n file marks (indicating a file break) to the data stored in the data buffer 21 to instruct the tape to write the data. When a write file mark command (count n) is received from the channel 4, all data stored in the data buffer 21 is written to the tape with n file marks thereafter. . It is also assumed that the function of disconnecting the input / output bus 5 from the input / output bus 5 during the data transfer of the 8 mm tape device 20 is prohibited.

Next, channel 4 of the computer system shown in FIG.
Is instructed twice from the CPU 1 to the channel 4 to write 100 KB data to the 8 mm tape device 20, and the operation is written from the BOT to the 8 mm tape loaded in the 8 mm tape device 20. The case will be described as an example, with reference to the flowchart in FIG. 1 and the operation explanatory diagram in FIG. First, the conventional method will be described.

When a first write instruction for the 8 mm tape device 20 is issued from the CPU 1 to the channel 4,
The designated 100 KB data is read from the main storage device 2. Next, the channel 4 is connected via the input / output bus 5 to FIG.
As shown in (b), the first write command output (B1) is performed to the 8 mm tape device 20, and then the first write data transfer (B2) to the 8 mm tape device 20 is performed.

When the 8 mm tape device 20 receives the write command from the channel 4, the 8 mm tape device 20 transfers the next 100K.
The write data of B is sequentially stored in the data buffer 21. Since the amount of data stored in the data buffer 21 has not reached the reference amount of 128 KB for writing to the tape, the operation corresponding to the write command is completed when 100 KB is stored in the buffer 21 and the 8 mm tape device. As shown in FIG. 3B, a status (write status) notification (B3) of the execution result of the write command is performed from the channel 20 to the channel 4.

When a normal end of the write command operation is notified by the write status from the 8 mm tape device 20, the channel 4 notifies the CPU 1 to that effect.
Then, an 8 mm tape device 20 is transferred from the CPU 1 to the channel 4.
Is written for the second time, and channel 4
Reads the designated 100 KB data from the main storage device 2. Then, the channel 4 outputs a second write command (B4) to the 8 mm tape device 20 via the input / output bus 5 as shown in FIG. Is performed (B5).

During the second write data transfer,
The amount of data stored in the data buffer 21 is 128
Reach KB. Then, the 8 mm tape device 20 starts an operation for writing the write data stored in the data buffer 21 to the tape. At this time, assuming that the head of the 8 mm tape device 20 is located at the BOT, the actual writing to the tape is performed approximately 40 seconds after the 128 KB write data is stored in the data buffer 21. It is. Therefore, during this time, the second write data transfer (B5) is suspended, and the I / O bus 5
Is occupied by the interrupted write data transfer (B5) to the 8 mm tape device 20. Then, when the writing to the tape is actually started, the interrupted write data transfer is restarted and stored in the data buffer 21. Then, from the 8 mm tape device 20 to the channel 4, FIG.
As shown in (b), a status (write status) notification (B6) of the write command execution result is performed, and the input / output bus 5 is released.

The above is from CPU 1 to channel 4.
This is an operation according to the conventional method when writing of 100 KB data to the 8 mm tape device 20 is instructed twice in succession, and when writing to the tape from the data buffer 21 in the 8 mm tape device 20 becomes possible. From about 40 seconds,
The data transfer to the 8 mm tape device 20 occupies the input / output bus 5. Next, the method of this embodiment will be described.

When a first write instruction for the 8 mm tape device 20 is issued from the CPU 1 to the channel 4,
The designated 100 KB data is read from the main storage device 2. At this time, the channel 4 determines whether or not the head of the 8 mm tape device 20 is located at the BOT. This BO
The determination condition of being located at T is roughly divided into the following two. (1) After any of REWIND, LOAD and UNLOAD commands has been issued. (2) UNIT ATTENT from 8 mm tape device 20
ION (report of tape replacement or power cycling of the device)
After the status has returned.

The channel 4 is set to 8
When it is determined that the head of the mm tape device 20 is positioned at the BOT, the procedure shown in the flowchart of FIG.
The mm tape device 20 is controlled.

First, as shown in FIG. 3A, the channel 4 is connected to the 8 mm tape device 20 via the input / output bus 5.
The second write command output (A1) is performed (step S
1) Subsequently, the first write data transfer (A2) to the 8 mm tape device 20 is performed (step S2). Up to this point, it is the same as the conventional method.

When the 8 mm tape device 20 receives the write command from the channel 4, the 8 mm tape device 20 transfers the next 100K.
The write data of B is sequentially stored in the data buffer 21. Since the amount of data stored in the data buffer 21 has not reached the reference amount of 128 KB for writing to the tape, the operation corresponding to the write command is completed when 100 KB is stored in the buffer 21 and the 8 mm tape device. As shown in FIG. 3A, a status (write status) notification (A3) of a write command execution result is performed from channel 20 to channel 4.

When the channel 4 receives the write status from the 8 mm tape device 20 (step S3), it determines whether or not the write command operation has been normally completed based on the status (step S4). Fig. 3
As shown in (a), an output (A4) of a write file mark command specifying the count "0" (that is, specifying the number of file marks as "0") is performed on the 8 mm tape device 20 (step S5). .

An 8 mm tape device 20 generally has a channel 4
Receives a write file mark command specifying a count n from the buffer, retrieves the write data (here, 100 KB) stored in the data buffer 21 at that time, and thereafter retrieves the number of files specified by the count n of the file mark command. An operation for writing a mark on a tape is performed.

In this embodiment, the value of the count n of the file mark command given to the tape device 20 from the channel 4 by the writing when the head of the 8 mm tape device 20 is positioned at the BOT is as described above. Is "0". Therefore, the 8 mm tape device 20 performs an operation for taking out the write data (100 KB) stored in the data buffer 21 and writing the write data (here, from the BOT) onto the tape as it is (without attaching a file mark). .

Here, it takes about 40 seconds until the writing to the tape is actually performed, that is, until the write file mark command ends. However, during this time, channels 4 and 8
Since there is no data transfer to and from the mm tape device 20, the input / output bus 5 is not occupied by the 8mm tape device 20, and the channel 4 is connected to the other magneto-optical disk devices 6-9.
It is possible to input and output data to and from an external storage device that can be accessed at high speed.

When the 8 mm tape device 20 executes the write file mark command (designating the count “0”), the status (write) of the execution result of the write file mark command is given to the channel 4 as shown in FIG. (File mark status) notification (A5).

When the channel 4 receives the status of the write file mark from the 8 mm tape device 20 (step S6), it determines whether or not the write file mark command operation has been completed normally based on the status (step S7). If the writing is normally completed, it is determined that the writing of the write data from the BOT has been completed normally, and the CPU 1
Notify.

Then, the CPU 1 issues a second write instruction for the 8 mm tape device 20 to the channel 4, and the channel 4 reads the designated 100 KB data from the main storage device 2. In this case, since the head of the 8 mm tape device 20 is not located at the BOT, the channel 4 is
As in the conventional case, a second write command is output to the 8 mm tape device 20, and then a second write data transfer to the 8 mm tape device 20 is performed.

When the amount of write data specified by one write instruction from the CPU 1 exceeds the reference amount for writing data from the data buffer 21 to the tape, the head of the 8 mm tape device 20 is positioned at the BOT. In this case, the channel 4 divides the designated write data so that the amount of the first write data after the division is equal to or less than the reference amount, and outputs the write command (and the write data transfer) a plurality of times. What should be done separately. In this case, the output of the write file mark command specifying the count “0” after the first write command output (and the write data transfer) is the same as in the above embodiment.

Although writing to the 8 mm tape device 20 has been described above, the present invention can be similarly applied to writing to other magnetic tape devices such as a 1/4 inch cartridge tape device.

[0037]

As described in detail above, according to the present invention,
When data is written from the beginning of the tape of the magnetic tape device, a write command is output from the input / output channel device to the tape device in the first step to transfer the write data, and the data is transferred to the data buffer of the tape device. After the storage, a write file mark command designating the number of file marks “0” (count “0”) is output to the magnetic tape device in the second step.
By executing the first step, the data stored in the data buffer of the magnetic tape device can be forcibly written from the beginning of the magnetic tape without adding a file mark. Even if it takes a long time due to a mechanical problem of the tape device, the I / O bus does not need to be occupied by the magnetic tape device during that time. Therefore, during that time, input / output control between the input / output channel device and another external storage device that can be accessed at high speed, such as a magnetic disk device, can be performed without waste, and the performance of the entire system is improved.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a method for controlling an 8 mm tape device of an input / output channel device according to an embodiment of the present invention.

FIG. 2 is a system configuration diagram of a computer system including an input / output channel device to which the 8 mm tape device control method shown in the flowchart of FIG. 1 is applied.

FIG. 3 is a view for explaining an operation of the embodiment in comparison with a conventional system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... CPU, 2 ... Main memory, 3 ... System bus, 4 ...
Channel (input / output channel device), 5 ... input / output bus, 2
0: 8 mm tape device (magnetic tape device), 21: data buffer, S1, S2: step (first step),
S5: Step (second step).

Claims (1)

(57) [Claims] An external storage device including a magnetic tape device having a data buffer is connected via an input / output bus, and input / output between the external storage devices is executed via the input / output bus. in the output channel device, before
Start of magnetic tape loaded in magnetic tape unit
The data write at the time of the first write data transfer.
The amount of data transferred from the data buffer of the tape
A range that does not exceed the reference amount that allows writing to tape
To perform at least one write data transfer
A method for controlling a magnetic tape device of an input / output channel device.
Te, when writing data from the starting end of the magnetic tape, exceeds the reference amount to be written from the beginning
Write data from the I / O channel device
A write command is output to the magnetic tape device and transferred.
A first step of storing the data in the data buffer of the tape device, and writing n data marks on the magnetic tape by attaching n file marks to the data stored in the data buffer. By outputting a write file mark command for instructing the execution to the magnetic tape device with the value of the file mark number designating value n being “0”, the data of the magnetic tape device is executed by executing the first step. A second step of forcibly writing the data stored in the buffer from the beginning of the magnetic tape without adding a file mark
A method for controlling a magnetic tape device of an input / output channel device.