JPH0219541B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inter-reel tape drive device controlled by a host system in a magnetic tape control system, and more particularly to an inter-reel tape drive control device.

In a reel-to-reel tape drive,
IBG (Inter-Block-Gap)
If no new read or write commands are received while the read/write head is passing through the read/write head (i.e., before processing the next block of data), an overrun occurs (the read/write head A state in which the IBG distance is passed) occurs. When the above overrun occurs, the tape drive must return the tape to the IBG, and the inter-reel tape drive cannot execute instructions from the upper system during that time, reducing the efficiency of the magnetic tape subsystem. It will be dropped.

In the reel-to-reel tape drives proposed so far, this overrun frequency causes
Two methods were used: slowing down the tape speed or setting the IBG distance to twice the standard value.

However, reducing the tape speed significantly reduces the efficiency of the magnetic tape subsystem, and also increases the load on the magnetic tape drive by processing data at different speeds. These disadvantages include complicating the magnetic tape drive, reducing reliability and stability, complicating maintenance, and above all, increasing the cost of the magnetic tape drive.

In addition, the method of setting the IBG distance to a single value (twice the standard value) regardless of the operating mode or data processing form of the upper system does not work because commands from the upper system are frequently sent. In the case of the following operation mode, the amount of data that can be stored on one roll of tape decreases due to the longer IBG distance, and if the frequency of commands sent from the host system is low, overruns often occur. It has the disadvantage that it occurs.

The present invention provides a standard IBG value and a maximum permissible IBG value within a magnetic tape controller for data processing formats and operation modes.
The maximum allowable IBG value is given as two values and is calculated by counting the number of overruns caused by the magnetic tape drive within the magnetic tape subsystem.
The present invention provides an apparatus that solves the above drawbacks by correcting the IBG value and improves the efficiency of the magnetic tape subsystem.

According to the present invention, when writing data to tape, IBG is a standard value determined from compatibility with other devices and the maximum allowable value determined from the data amount of data processing of the system used. When the IBG value that changes depending on the timing of commands sent from the upper system is between the above two IBG values, the maximum IBG value is decreased, and the changing IBG value is set as the above two values. There is obtained an inter-reel tape drive control device characterized in that it is equipped with a device that increases the maximum IBG value depending on the frequency when the maximum IBG value falls outside the range of IBG values.

Here, "as the maximum allowable value determined from the amount of data processing of the system used"
"IBG" is the IBG determined below.

(1) By increasing the IBG, the amount of data that can fit on one tape is reduced.

(2) In general, the amount of data processed in a certain system often takes a nearly constant value if the utility used by the system is the same.

(3) Therefore, use the above utilities, etc.
To make the number of tape rolls required for a job permissible for the system, IBG in section (1)
The maximum value is naturally determined by the relationship with item (2).

In the present invention, the maximum allowable
The efficiency of the magnetic tape subsystem is improved by changing the IBG value according to the history of commands sent from the higher-level system and reducing overrun conditions on the magnetic tape.

Embodiments of the magnetic tape control system according to the present invention will be described below with reference to the drawings.

In FIG. 1, command 19 from the upper system
is given to the command detection control circuit 2, and the command detection control circuit 2 receives the command and outputs the servo circuit 10.
Also, the write circuit 16 or the read circuit 12 is activated.

In addition to this normal magnetic tape device operation command, the IBG distance register 8 is a standard IBG distance register.
and/or the maximum IBG distance allowed. In this case, it is sometimes given by a command from the higher-level system, and sometimes specified by an external switch. For example, the value of IBG distance register 8 when the power is turned on is 7.62 in GCR mode of a 1/2 inch magnetic tape device.
The standard value is 15.24mm for mm, PE, and NRZ9TR modes, and 15.24mm for cartridge devices, and the maximum allowable IBG value is initialized to several times that value.

Now, in response to a write-related command, the write circuit 16 writes data onto the tape via the write head 17. The read head 13 reads the written data on the tape, and the data is waveform-shaped by the read circuit 12 and applied to the IBG detection circuit 9 and the block detection circuit 1.

Now, in FIG. 2, it is assumed that the nth block 31 has been written on the tape and the tape is running. If the maximum IBG distance allowed in IBG distance register 8 is represented by 34, then if an instruction is given by the host system when the read/write head is at position 32, then n+
The first block has a predetermined value from the nth block.
Since only IBG is written apart, overrun will not occur. If the read/write head is not given a command from the host system even if it exceeds the maximum IBG distance that it is allowed to take, represented by 34,
For example, an overrun occurs when the read/write head is at position 33.

Returning to FIG. 1, overrun detector 4 detects the above-mentioned overrun, and overrun counter 5 counts the number of times this overrun has occurred within a certain period of time. On the other hand, the block counter 3 counts the number of blocks processed within a certain period of time. The comparison calculator 6 uses the value of the block counter 3 and the value of the overrun counter 5 to determine whether to lengthen or shorten the maximum allowable IBG value. When the comparator 6 completes the calculation, it uses the IBG distance decrease signal 14 and the IBG distance increase signal 15.
By changing the value of the IBG distance register 8, the IBG value is controlled so that the efficiency of the magnetic tape subsystem increases and the amount of data that can fit into one roll of magnetic tape increases.

Through the above control, the magnetic tape device can write data with better performance than ever before. On the other hand, during reading, even after reading the n-th block, the magnetic tape drive continues to receive a reading command. That is, when reading data from a tape, the tape drive is run after reading a designated block until reading the next block. This allows data to be read efficiently by the next read command (by setting the IBG value to the maximum value allowed by the above system, the read head will rush into the next data block during reading). This method increases the probability of receiving the next read command before reading data on the tape in a short period of time without repositioning the tape due to read overrun.

Although it depends on how commands are issued from the host system, this control method can achieve great performance in inter-reel tape drives.

As described above, according to the present invention, it is possible to provide an efficient data processing method in a magnetic tape subsystem, and to obtain an inexpensive and highly reliable magnetic tape drive device and its control device.

[Brief explanation of drawings]

Figure 1 is a block diagram of the circuit for obtaining the control method of the present invention, and Figure 2 is a block diagram of the circuit on the tape.
It is an explanatory diagram showing IBG and overrun operation. 1...Block detection circuit, 2...Command detection control circuit, 3...Block counter, 4...Overrun detector, 5...Overrun counter, 6...Comparison calculator, 7...Tape position Control circuit, 8...
IBG distance register, 9...IBG detection circuit, 10...
... Servo circuit, 11 ... Motor, 12 ... Read circuit, 13 ... Read head, 14 ... IBG distance decrease signal, 15 ... IBG distance increase signal, 16 ...
Write circuit, 17...Write head, 18...
IBG distance set signal, 19... Command from upper system, 30... n-1th block, 31...
...nth block, 32, 33...read, write head, 34...maximum allowed to take
IBG distance.

Claims (1)

[Claims] 1 When writing data to tape, standard values determined from compatibility with other devices.
IBG and IBG as the maximum allowed value determined from the data volume of the data processing of the system used
The IBG value that changes depending on the timing of commands sent from the upper system is the above binary IBG.
Equipped with a device that reduces the maximum IBG value when it is within the range between the two values, and increases the maximum IBG value depending on the frequency when the changing IBG value falls outside the above two IBG values. Features: Inter-reel tape drive control device.