JPS63133305A - Error recovery controlling system for magnetic tape file - Google Patents

Abstract

PURPOSE:To exactly execute an error recovery control by repositioning a magnetic head, when an error is generated in the course of write, and thereafter, comparing the contents of a data block immediately before, with a data block which has been written normally in the end, in a saving storage area. CONSTITUTION:When a data block is written normally to a magnetic tape file, the contents of a prescribed position of the data block which has been written normally are saved in a saving storage area of a storage means 2 in a main storage device 5. Subsequently, when an error is generated in the course of write, a magnetic head is repositioned, and thereafter, the contents of a prescribed position in the data block immediately before the present head position, and the contents of the same prescribed position in the data block which has been saved in the means 2 and has been written normally in the end are compared by a comparing means 3. Only when a result of comparison shows coincidence, retrying by a write means 4 is executed. In such a way, an error recovery control can be executed exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control system for error recovery when a write error occurs in a magnetic tape file used in a computer system.

[Conventional technology]

-m, when writing data to a magnetic tape file,
Each time a data block is written, it is determined whether the writing was completed normally or not. If a writing error occurs, the operating system moves the magnetic head to the position in the magnetic tape file immediately before writing that data block. Reposition the target so that it appears and retry error recovery.

Conventionally, the above-mentioned positioning of a magnetic tape file, which is necessary for recovering from an error that occurs during writing to a magnetic tape file, has been performed by skipping one data block in the backward direction.

[Problem that the invention seeks to solve]

However, in the conventional method described above, the contents of the skipped block cannot be read, so the validity of the positioning cannot be confirmed.

Therefore, if the magnetic tape in the part of the data block where the error occurred is in a bad state of magnetization, the data block where the error occurred is not recognized as a data block by the magnetic tape device, and the immediately preceding normal data block is It may be skipped or positioned in the center of a data block, resulting in a successfully written data block being lost or an invalid data block remaining even after a successful retry write. There were drawbacks.

The present invention has been made in view of the above-mentioned conventional circumstances, and
SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a new error recovery control system for magnetic tape files which makes it possible to overcome the above-mentioned drawbacks inherent in the prior art.

[Means for solving problems]

In order to achieve the above object, a magnetic tape file error recovery control method according to the present invention provides a magnetic tape file error recovery control method in a computer system in which an operating system repositions a magnetic head with respect to a magnetic tape file at the time of a write error. The recovery control method includes: an evacuation storage area; and an evacuation that, when a data block is successfully written to a magnetic tape file, saves the contents at a predetermined position in the normally written data block to the evacuation storage area. means for comparing the contents of a predetermined position in the data block immediately preceding the current head position with the contents saved in the save storage area, the repositioning by the operating system being activated later; and a writing means for retrying writing only when the comparison result of the comparing means indicates a match.

[Effect]

When a data block is normally written to the magnetic tape file, the contents of a predetermined position of the normally written data block are saved to the save storage area by the save means.

If an error occurs while writing the next data block after a successfully written data block, the operating system repositions the magnetic head by skipping the data block in which the error occurred one block in the opposite direction, as in the past. Ru.

After this repositioning, the comparison means compares the content at a predetermined position in the data block immediately before the current head position with the same predetermined position in the last successfully written data block that was saved in the save storage area. The contents of

Therefore, if the repositioning by the operating system is correct, the comparison means will detect a comparison match; If an incorrect repositioning has been performed, such as when a match has been made, the comparing means will not be able to detect a match, and therefore the writing means will retry writing only when the comparing means indicates a match.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

Referring to FIG. 1, the embodiment of the present invention has storage means 2 including a backup storage area allocated for each magnetic tape device.
Then, only when writing of the data block to the magnetic tape file is successfully completed, the content of a predetermined length, for example, 1 byte, at a predetermined position of the normally completed data block is allocated to the magnetic tape device in the storage means 2. A saving means 1 is activated by the operating system to save the content of the byte at a predetermined position in the data block immediately before the current magnetic head position and is allocated to the magnetic tape device in the storage means 2. a comparison means 3 that compares the contents of the bytes saved in the saved storage area, and a writing means 4 that re-attempts writing only when the comparison result of the comparison means 3 indicates a match. It is configured. In FIG. 1, a part of the main storage device 5 is allocated to the storage means 2.

FIG. 2 is a flow chart showing a processing example of the saving means 1 shown in FIG. Referring to FIG. 2, the saving means 1 performs device status byte input processing 11. Device status byte determination processing 12.
Successive byte succession processing at a predetermined position within a data block 13. and save storage $I area write processing 14.

FIG. 3 is a flowchart showing a processing example of the comparing means 3 shown in FIG. Referring to FIG. 3, the comparison means 3 performs the backward reading skip processing 31. Forward successive processing 32. Successive byte succession processing at predetermined positions within data block 33. Continuation of bytes in the save storage area 34. It is configured to perform byte comparison processing 35° and comparison result output processing 36.

FIG. 4 is a flowchart showing an example of processing by the writing means 4 shown in FIG. Referring to FIG. 4, the writing means 4 performs a comparison result input process 41. Comparison result determination process 42. and write retry processing 43.

FIG. 5 shows an example of the configuration of the storage means 2 shown in FIG. It is configured to have each of the storage head E1 to EN as a save storage area.

Next, the operation of this embodiment will be explained in detail with reference to the drawings.

First, the saving means 1 sequentially outputs the device status byte from the magnetic tape device #j for which the write command has been completed through the device status byte input process 11, and then through the device status byte determination process 12.
It is determined whether or not the bit configuration of this device status byte indicates that the current data block DI-+ has been written normally. Byte Bt-+ at a predetermined position in the data block DI-1 that is the write target on the main memory is successively written by the predetermined position byte successive processing 13, and the save storage area write processing is performed! 4, the data is written to the evacuation storage area indexed by the device number of the magnetic tape device #j in the storage means 2, and if the bit configuration indicates that the data was written abnormally, steps 13 and 14 are skipped. do.

Then the next data block D! to the magnetic tape file!
If a write error occurs, the operating system processes the location of the magnetic tape file, as in the conventional case, and then the operating system activates the comparing means 3. When the comparing means 3 is activated, it skips the previous one data block in the backward direction by the backward skipping process 31 as shown in FIG. 3. Referring to FIG. is at position 61 in the same figure, and if the data block DI-1, which has just been successfully written, is at position 63 in the same figure, the magnetic head is repositioned by the operating system to position 64 in the figure, As a result of the above-mentioned backward reading skip processing 31, the position 62 in the figure is reached.

Next, the comparing means 3 reads one data block in the forward direction by a forward successive process 32, and performs a byte successive process 33 at a predetermined position within the data block to read out the data block D, -1 by the forward successive process 32. Bytes St-+ at a predetermined position in the storage means 2 are successively stored, and bytes Br-+ in the save storage area indexed by the magnetic tape device number in the storage means 2 are successively stored by a byte succession process 34 in the storage area.
Byte B1-1 read out by the byte comparison process 35 at a predetermined position within the data block byte succession process 33
and byte B read in the storage area byte read processing 34.
+−+ and outputs the comparison result by comparison result output processing 36.

Next, the writing means 4 inputs the output of the comparison result output processing of the comparison means 3 through a comparison result input processing 41, determines whether the comparison result represents a match or a mismatch, and determines whether the comparison result represents a match or a match. If so, the write command is retried by write retry processing 43. If it indicates a mismatch, the write retry process 43 is not performed and, for example, a program abnormal termination message is output to the console.

Referring to FIG. 6, data block D at location 63
. come into position. At this time, if the contents of the byte B+-+ at the predetermined position in the data block DI-1 match the contents of the byte B+-+ saved in the save storage area, the data block Di-+ is normal. This indicates that the position of the magnetic head shown in FIG. 64 is correct.

Although the above embodiments apply the present invention to error recovery control of magnetic tape files in a plurality of magnetic tape devices, it is of course applicable to a computer system equipped with a single magnetic tape device. In that case, only one evacuation storage area is required.

(Effects of the Invention) As described above, according to the present invention, the validity of positioning for retrying recovery from a write error in a magnetic tape file is determined by the data block written immediately before the positioned head. You can confirm that it is the last data block written normally by referring to the contents of a certain size at a specific position without including positional information such as a sequence number in advance in the data, so it can be written in any format. This has the effect of preventing the loss of data blocks and the remaining of invalid data blocks in magnetic tape files.

[Brief explanation of the drawing]

1 is a block diagram of an embodiment of the present invention, FIG. 2 is a flowchart of an example of processing by saving means 1, FIG. 3 is a flowchart of an example of processing by comparison means 3, and FIG. 4 is an example of processing by writing means 4. 5 is a diagram showing an example of the configuration of the storage means 2, and FIG. 6 is an explanatory diagram of the operation of the embodiment of the present invention. In the figure, 1... saving means, 2... storage means, 3
. . . comparison means, 4 . . writing means, 5 . . . main storage device.

Claims (1)

[Scope of Claim] An error recovery control method for a magnetic tape file in a computer system in which an operating system repositions a magnetic head with respect to a magnetic tape file in the event of a write error, comprising: an evacuation storage area and data to the magnetic tape file. a saving means for saving the contents at a predetermined position in the normally written data block to the saving storage area when writing of the block is normally performed; Comparing means for comparing the content at a predetermined position in the data block immediately before the head position with the content saved in the save storage area, and writing only when the comparison result of the comparing means indicates a match. An error recovery control method for a magnetic tape file, comprising a writing means for performing a retry.