JPS5944694B2 - Magnetic tape control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a magnetic tape control system, in particular, a block serial number memory for storing serial numbers of blocks whose processing has been completed or is in the middle of execution when a power-off state occurs. This invention relates to a magnetic tape control system in which, when turned on, the next write or read process is restarted from the block position of the serial number given by the contents of the block serial number memory.

Conventionally, problems have arisen in write or read processing for magnetic tape devices after an abnormal power outage such as a power outage, a momentary power outage, or a power outage due to an erroneous operation.

In other words, if write processing or read processing is executed from several blocks before the power is turned on again, the write data that was partially written at the time of the power outage will not remain on the medium, but if the write processing has already been completed. It is necessary to hold data for multiple blocks. The present invention aims to solve the above-mentioned problems, and is capable of finding the position of a block where processing has finished or was in the middle of execution when the power is turned off, and executing processing or read processing from that block position to a lie. It is intended to be.

Furthermore, it is an object of the present invention to reduce the processing burden on the host side when moving the magnetic tape in the reverse direction in finding the position of the block where the processing was completed or in the middle of execution when the power was turned off. Therefore, the magnetic tape control method of the present invention is designed to prevent a power-off state from occurring in a magnetic tape system having a magnetic tape device that executes write processing or read processing in units of blocks based on write or read instructions. It is equipped with a power outage memory that stores the serial number of the block position where the processing was completed or was in the middle of execution when the power was cut off, and corresponds to each program when writing to the magnetic tape device. When the power is turned on again with the power failure memory indicating that a power-off state has occurred, the magnetic tape device is once set in the write processing direction or the read processing direction. The program is moved in the opposite direction for a predetermined time by a timer, and then the check/read processing is executed in the forward direction, and the program serial number information corresponding to the check/read processing and the contents of the program serial number memory are It is characterized in that it is controlled to execute write processing or read processing from the matched block position. This will be explained below with reference to the drawings. FIG. 1 is an overall diagram of an embodiment of a system to which the magnetic tape control method of the present invention is applied, FIG. 2 is an explanatory diagram conceptually explaining the power failure memory and serial number memory according to the present invention, and FIG. Flowchart of an Embodiment of the Magnetic Tape Control Method of the Invention. FIG. 4 shows the configuration of essential parts of an embodiment used in the magnetic tape control method of the invention.

In Figure 1, 1 is the central processing unit, 2 is the magnetic tape
Force setting control device, 3, magnetic tape/force setting device, 4
Reference numeral 5 indicates a memory device, 5 indicates a memory section that constitutes a power outage memory or a serial number memory, and 6 indicates a battery (not shown) that prevents at least the contents of the memory section 5 from disappearing in the event of a power outage. .

In addition, in FIG. 2, 5 and 6 correspond to those in FIG. 1, and 7
8 represents a power failure memory that stores the occurrence of a power-off state, and 8 represents a program serial number memory that stores the serial number of a program that has completed processing or was in the middle of execution when the power-off state occurred. ing. Write processing or read processing for the magnetic tape/force setting device 3 is performed in units of programs according to instructions from the central processing unit 1. Then, a block serial number is assigned to the block unit, and when a write process or a read process is completed for one block, the contents of the block serial number counter are updated. Also, during write processing, each
The contents of the program serial number counter are recorded on the magnetic tape/force setting device in correspondence with the program. When the commercial power supply (not shown) is cut off while the write processing or read processing is being performed or is being performed as described above, the central processing unit 1 detects this and reports the occurrence of the cutoff state to the power outage. The contents of the program serial number counter are stored in the serial number memory 8.

When the commercial power supply is cut off, the power is turned on again by, for example, an in-house power generator, but the contents of the power failure memory 7 and the serial number memory 8 are not erased while the power supply is cut off. can be made.

When the power is turned on again, the following control is performed as shown in the flow chart shown in FIG.

That is, (1) When the power is turned on, it is checked by process A whether a power-off state has occurred first.

(2) If the power is cut off, the magnetic tape
The force setting is performed using the magnetic tape/force setting device 3 shown in FIG.
It is checked by process B whether or not it is set to . (
3) If it is assumed that the power setting has been set normally, the process C will cause the process to be completed before the power is turned off, or to perform a number of operations in the opposite direction to the write process direction or read process direction that was in progress before the power was turned off. The block will be reversed.

(4) When the reverse is completed, read processing is performed in the reverse direction of the reverse, ie, in the forward direction, in process D.

(5) Then, when it is detected by process E that the block position of the serial number given by the contents of the serial number memory 8 has been reached, process F determines whether the program was terminated immediately before the power was turned off or not. It is checked whether the process being executed at the time of disconnection was a read process or a write process.

(6) If it is a write process, it is checked in process G whether the write process was actually in progress when the power was turned off.

(7) If it is in the middle of execution, by process H,
Write processing is performed from the beginning of the middle block.

(8) If it is determined by the above process F that a read process was performed, it is checked in process 1 whether or not a read process was actually in progress when the power was turned off.

(9) If it is in the middle of execution, by process J,
Read processing is performed from the beginning of the middle block.

(Self) If the process has been completed by the above process G or I, it goes without saying that the write process or read process will be performed from the next block.

FIG. 4 shows an embodiment of the configuration of a portion that executes the above-mentioned processes C to E.

Reference numerals 7 and 8 in the figure correspond to those in FIG. 2, 9 and 10 are flip-flops, 11 is a timer that measures the reverse execution time, 12 is a comparison circuit, and 13 is an AND circuit. There is. As outlined with reference to FIG. 1, when a power-off state occurs, the central processing unit 1 sets the occurrence of the power-off state and stores the contents of a block serial number counter (not shown) in the block serial number memory 8.

When the power is turned on again in this state, the AND circuit 13
is turned on and flip-flop 9 is set. That is, a reverse operation corresponding to process C shown in FIG. 3 is performed. Then, the timer 11 measures the reverse execution time. When the timer 11 times up, the flip-flop 9 is reset to stop the reverse operation, while the flip-flop 10 is set to issue a forward instruction corresponding to the process D. Processing D
During the read process corresponding to , the contents of the unillustrated program serial number counter (or the program serial number information read from the magnetic tape medium) are compared with the contents of the program serial number memory 8. When the comparator circuit 12 issues a match signal, the flip-flop 10 is reset;
The above forward instruction is stopped. Although not shown in the figure, when the above power-off state occurs, (1) whether the process that was completed immediately before or was currently being executed was a write process or a read process is held; If it is in the middle of execution, this information is retained.

Based on the information from (i) and (4),
Processes corresponding to processes F, G, H, I, and J shown in FIG. 3 are executed. As described above, according to the present invention, when the power is turned on again after a power-off state occurs, write processing or read processing can be performed from the block position where it was when the power-off state occurred.

Therefore, it is not necessary to store write data across multiple programs when executing normal write processing, for example. Furthermore, even if write processing or read processing is in progress when the above disconnection occurs, the program will be restarted from the beginning of the program, so undesired information will not remain on the tape medium due to the write processing after restarting. or errors will not occur in read processing after restarting.

[Brief explanation of the drawing]

FIG. 1 is an overall diagram of an embodiment of a system to which the magnetic tape control method of the present invention is applied, FIG. 2 is an explanatory diagram conceptually explaining the power failure memory and serial number memory according to the present invention, and FIG. A flowchart of an embodiment of the magnetic tape control method of the invention,
FIG. 4 shows a block diagram of essential parts of an embodiment used in the magnetic tape control system of the present invention. In the figure, 1 is a central processing unit, 2 is a magnetic tape/force setting control device, 3 is a magnetic tape/force setting device, 4 is a memory device, 5 is a memory section, 6 is a battery, 7 is a power failure memory, 8
1 is a block serial number memory, 9 and 10 are flip-flops, 11 is a timer, and 12 is a comparison circuit.

Claims (1)

[Claims] 1. In a magnetic tape system having a magnetic tape device that executes write processing or read processing in units of blocks based on a write instruction or read instruction, it is stored that a power-off state has occurred. It is equipped with a power failure memory and a block serial number memory that stores the serial number of the block position where the processing was completed or in the middle of execution when the power was cut off, and also stores the block serial number corresponding to each block during write processing to the magnetic tape device. When the power is turned on again with the power failure memory indicating that a power-off state has occurred, the magnetic tape device is temporarily moved in the opposite direction to the write processing direction or the read processing direction. The block position is moved by a timer for a predetermined period of time, and then the check read process is executed in the forward direction, and the block serial number information corresponding to the check read process matches the contents of the block serial number memory. A magnetic tape control method characterized in that the magnetic tape is controlled to perform write processing or read processing. 2. The magnetic tape control system according to claim 1, wherein the contents of the power failure memory and the block serial number memory are configured so that they do not disappear when the power is turned off. 3. The magnetic tape system is configured to remember whether or not a write process or a read process was currently in progress at the time of the occurrence of the power-off state, and is configured to remember whether or not a write process or a read process was currently in progress when the power-off state occurred, and to resume the write process or read process when the power is turned on. 3. The magnetic tape control system according to claim 1, wherein the write process or read process is executed from the beginning of the block position where the coincidence occurs.