JPH02226350A - Data control method for computer system - Google Patents

Abstract

PURPOSE:To easily discover the presence and absence of destruction in operating system (OS) control information by computing a check sum by a check sum table before a directory is updated on a memory, and detecting the destruction of data for each block. CONSTITUTION:In the internal part of a memory 2 to which the directory, etc., read from a disk 1 is temporarily stored, a check sum table 13 is set. The computation of the check sum is executed for each directory block based on a sum value recorded to each area of the check sum table 13. Just before the OS updates the contents of a directory 12 on the memory, the check sum of the directory block including an objective entry is computed and compared with the sum value which is computed after the preceding update. When the two sum values are different, it is judged that the data in the directory block are destroyed. Then, an error message is displayed and processing is interrupted. Thus, in the control information of the OS, the presence and absence of the destruction can be easily detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data management method for a computer system in which files stored in an external storage device such as a magnetic disk are managed by a library 113m.

[Conventional technology]

The functions of computer application systems, such as computer systems, are controlled by software programs loaded into memory.

This software program is divided into a system program called O8 (operating system) and an application program that implements individual functions for each system. O8 provides functions commonly used by each application program,
It manages the hardware and software resources of the system and provides an appropriate execution environment for application programs.

By the way, in small-scale computer systems, multiple application programs do not run at the same time.
Many tasks can only be executed once (single task).

Moreover, in this case, the O8 and the application program often operate in the same mode from a hardware perspective. This is because in small-scale systems, application programs often use O8 management information, so in order to improve system execution efficiency, application programs can directly access O8 management information. In large-scale systems, a hardware protection mechanism is provided to prevent O8 management information from being destroyed by an application program, but in the above-mentioned small-scale system, no protection mechanism is provided due to cost considerations.

Therefore, when an application program accesses O8 management information in a small-scale system, extreme care must be taken not to destroy the management information.

[Problems to be Solved by the Invention] However, even if the application program is considered to be finally completed, there is a risk that O8 management information may be accidentally destroyed due to a latent bug. In this case, if the destroyed management information is saved as is on the disk, it will require a great deal of effort and time to recover the pig, and it will also cause new system destruction, making it difficult to recover the entire system. There was a problem with this.

An object of the present invention is to provide a data management method that can easily detect whether or not O8 management information has been destroyed in a small scale system without a hardware protection mechanism.

[Issues to be solved]

In order to solve the above problems, the pig management method according to the present invention divides a directory in memory into a plurality of directory blocks, sets a checksum table corresponding to each directory block, and stores the contents of the directory in memory. Before updating, the checksum of the directory block is calculated using the checksum table, and data corruption is detected for each block.

[Effect]

When the system is started up, the checksum of the first directory is calculated, and after the application program is executed, the checksum of the directory is calculated again and compared with the sum value calculated before the program is executed. At this time,
If the two values do not match, it means that the data in that directory block has been destroyed. Since the checksum is calculated for each directory block, data corruption can be detected quickly. Furthermore, if the sum values match, the contents of the directory are rewritten as necessary, and the checksum of that directory block is calculated and recorded in the checksum table. The newly recorded sum value becomes the reference value when performing the next checksum calculation.

(Embodiment) An embodiment of the pig management method for a computer system according to the present invention will be described below.

FIG. 2 is a block diagram showing the basic configuration of a word calculator system for implementing the data management method according to the present invention. In FIG. 2, 1 is a disk in which files, their directories, and each program are stored, and 2 is a memory in which directories read from the disk 1 are temporarily stored. Thumb table is set. 3 is a CPU (central processing unit) that controls the entire system and performs various arithmetic processing; 4 is a keyboard; 5 is a display; 6 is an I10 bus.

FIG. 1 is a schematic diagram showing the relationship between the above-mentioned directories and checksum tables. In this embodiment, the O8 management information is directory information that forms the core of the file management system that is a part of the O8.

In FIG. 1, directory-1 on the disk is made up of a plurality of sectors, and in this example, every two sectors are accessed. Directory-2 read into the memory is composed of a plurality of directory blocks each having five directory entries as a unit, and one directory block stores two sectors worth of directories of directory-1. Furthermore, one directory block corresponds to each area of the checksum table 13, and checksum calculation is performed for each directory block based on the sum value recorded in each area of the checksum table 13. be exposed.

Note that one directory entry of a directory block stores management information regarding one file.

In the above configuration, to detect data corruption in the directory, first, immediately before O8 updates the contents of directory 12 in memory, it calculates the checksum of the directory block containing the target entry, and then calculates the checksum after the previous update. checksum value (this value is recorded in the checksum table). If the two sum values are different, it is determined that the directory block has been destroyed, an error message is displayed, and the process is interrupted. Furthermore, if the sum values are the same, it is determined that the directory block is normal, and necessary update work is performed. Then, a checksum is calculated for the rewritten directory, and this is recorded in the checksum table 13 as a new checksum value.

Next, the above-mentioned thumb check processing procedure will be explained based on the flowchart of FIG. 3 while referring to FIGS. 1 and 2.

First, before performing a thumb check, CPU3
Take out the pig in directory 12 stored in
Load it into memory 2.

Next, the CPU 3 obtains the entry number of the directory 12 from the file name of the file to be accessed (step 101). The directory block number is then calculated from this entry number (step 102).

Next, the checksum of the directory block is calculated and compared with the previous sum value recorded in the corresponding area of the checksum table 13 (step 103).
.

Then, it is determined whether the two values match (step 104). Here, if the two values match, it is determined that the checksum value is normal, and processing by the application program is executed (step 105).
. On the other hand, if the two values do not match in step 104, it is determined that the data in the directory is corrupted, an error message is displayed on the display 5, and the process is interrupted (step 106).

When the processing by the application program is completed (step 107), the CPU 3 calculates the checksum of the directory block again and uses the checksum table 1.
It is compared with the sum value recorded in the corresponding area of No. 3 (step 108).

Then, it is determined whether the two values match (step 109). Here, if the two values match, it is assumed that the data in the directory has not been destroyed, and the contents of the directory entry are rewritten as necessary (
Step 110). Next, the CPU 3 calculates the checksum of the directory block including the rewritten directory entry, and records it as a new sum value in the corresponding area of the checksum table 13 (step 111).

Then, the data in the directory 12 on the memory is stored on the disk 2 as necessary (step 112).

On the other hand, if the two values do not match in step 109, it is determined that the data in the directory is corrupted, 1 error message is displayed on the display 5, and the process is interrupted (step 106).

In the embodiment described above, one directory block contains
Although an example has been described in which two sectors of a disk correspond to one another, the present invention is not limited to this, and one directory block may correspond to a plurality of sectors. Furthermore, the number of directory blocks corresponding to a sector is not limited to one; for example, one sector may be associated with a plurality of directory blocks. Note that in order to shorten the time for checksum calculation, directory blocks and sectors may be associated on a one-to-one basis. As a result, so-called overhead can be minimized, and the efficiency of the system can be improved.

[Effects of the Invention] As explained above, in the data management method according to the present invention, before updating a directory on the memory, a checksum is calculated using the checksum table, and data is checked for data corruption for each block. Since this is configured to detect whether the O8 management information has been destroyed by an application program, it can be easily discovered. Therefore, when directory information updated in memory is stored on disk, directory information that is accidentally destroyed in memory is not stored on disk as is, which prevents the occurrence of so-called system downtime. be able to.

1...Disk, 2...Memory, 3...CPU,
4...Keyboard, 5...Display, 6...I
10 bus, 11... directory on disk, 12
...Directory in memory, 13...Checksum table.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the relationship between a directory and a checksum table, Fig. 2 is a block diagram showing the basic configuration of a tear sieve system for carrying out the data management method according to the present invention, and Fig. 3 is a schematic diagram showing the relationship between a directory and a checksum table. It is a flowchart showing a processing procedure.

Claims (1)

[Claims] In a computer system in which files are managed by a directory structure, a directory in memory is divided into a plurality of blocks, a checksum table corresponding to each block is set, and the directory is updated in memory. 1. A method for managing data in a computer system, comprising: calculating a checksum of the directory using the checksum table, and detecting data corruption for each block.