JPS63289657A - Common file access system - Google Patents

Abstract

PURPOSE:To speed up accessing operation and to improve the using efficiency of a line by forming an access management table for managing accesses to files of respective terminals in a host computer and forming a table for managing the copy of a common file and its copying state in each terminal. CONSTITUTION:Each terminal equipment 2 is provided with a common file 4, a common file copy storing device 23 for storing the copy of a partial block of the common file 4 and a table 24 for managing the updating state of the block copy in each block. In response to an access request to the files 4, 5 a block copy in the device 23 generating the access request is retrieved by the table 24 in the self-device. When an objective block copy exists, the copy is read out or rewritten and updated to update the corresponding block of the files 4, 5. Then, the updating of the block is informed to the equipment 2 using the block copy corresponding to the updated block based on the management table 13 in the host computer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a shared file access method, and more particularly to a shared file access method in which a plurality of terminal devices access a shared file owned by a host computer via a communication line.

Prior Art In a conventional system that employs this type of shared file access method, the shared file is held only in the host computer, and each terminal device accesses the shared file via a communication line every time a shared file access request occurs. accesses shared files on the host computer.

In the conventional shared file access method described above, since access to files is always performed via a communication line, there is a drawback that the speed of access to a file is limited by the speed of the communication line. In addition, since files are transferred via communication lines for each access request, when accessing the same file repeatedly, the same data is repeatedly sent over the communication line, which can be very difficult. The drawback is that it is wasteful.

Purpose of the Invention The present invention has been made to solve these drawbacks of the prior art, and its purpose is to speed up access to shared files and minimize data transferred over communication lines. The objective is to provide a shared file access method that enables

Structure of the Invention According to the present invention, there is provided a shared file access method in which a plurality of terminal devices access a shared file owned by a host computer via a communication line. A management table is provided to manage the access status from the terminal device for each fixed block of the shared file, and each of the terminal devices includes a storage means for storing a copy of a partial block of the shared file, and a storage means for storing a copy of a partial block of the shared file. Update letter! l! In response to an access request to the shared file, a block copy in the storage means in the terminal device that generated the access request is searched by the management table in the own device, and If a block copy exists, it is read or rewritten and updated, and in response to the update of this block copy, the corresponding block of the shared file is updated, and the updated block is updated according to the management table in the host computer. A shared file access system is obtained, characterized in that a block update notification is sent to a terminal device that uses a block copy corresponding to the block.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a system block diagram of an embodiment of the present invention, in which a host computer 1 and a terminal device 2 are interconnected through a communication line 3, and only one terminal device is shown in the figure. However, it is assumed that a plurality of terminal devices are connected to the host computer 1 via the communication line 3. Each of these terminal devices 2 can freely access shared files 4 and 5 connected to the host computer 1 via a communication line 3.

The host computer 1 includes a CPU 11, a transmitter/receiver 12, and a management table 13. The management table 13 is provided on the memory within the host computer, and is a table for recording access status from each terminal to the shared file. This management table 13 is shown in FIG.
As shown in , for each block of shared files 4 and 5, the ID (identification number) of each block, the status display (ST) of that block, the ID of the terminal accessing it, and its access rights (write/write/ Read access.

R/W> recording sections.

Note that the shared files 4 and 5 are managed in blocks of a fixed size, and each block is assigned a block ID.

The terminal device 2 includes a CPU 21, a transmitting/receiving section 22, a shared file copying section 23, and a management table 24.

The shared file copy unit 23 is a memory that stores copies of part of the shared files 4 and 5 in blocks, and the management table 24 manages the update status of copies of the shared files in blocks.

As shown in FIG. 2(B), this management table 24 includes the block ID of the copy of the shared file and its status (ST
).

FIG. 2 is a flowchart showing the file access procedure of the embodiment shown in FIG. When a request to access a shared file is generated from a terminal device (step 31
), the terminal device uses its own management table 24 to determine whether a copy of the corresponding block exists in the memory 23 within the terminal device. This determination is made while searching by referring to the management table 24 (step 32). If a copy of the file exists in the memory 23, access will be initiated within the own device.

If a copy of the file does not exist in the memory 23, a request is made to the host to transfer the corresponding block, but at this time it is determined whether there is free space in the memory 23 (step 33), and if there is free space, the file is transferred. A transfer request is made (step 34), and in response, the host transfers the file for which access is requested. At this time, the host checks the access rights of the terminal device and the contention state of write access using the management table 13, and if the corresponding block is not being accessed, the ID of this block, the ID of the terminal that issued the access request, and The access right is added to the management table 13 (step 35).

If the corresponding block is being accessed, table 13 has already been accessed.
After newly adding the TD and access rights of the terminal that issued the request to the access information existing in the file, the file is transferred to the terminal device. When the terminal device side receives this file, it stores it in the memory 23 and registers the block ID in the management table 24 (step 36).

If there is no free space in the memory 23 to create a copy of the file, the terminal device requests the post side to receive the block of the file that has not been received after the write access has been completed (step 37).

Upon receiving this request, the host side receives the file transfer from the terminal and updates the shared file and the management table 13 (step 38). The terminal side updates the management table of the taken block (step 39), and only then requests the host to transfer the file to be accessed (step 34).

If the access request is a write access (step 40), write access is made to the corresponding block in the memory 23, and a transmission notification is issued to the host (step 4).
1). Upon receiving this notification, the host records the invalidity of the block in the management table 13, and notifies the terminal that is using the block of the file update (step 42). Transfer of modified files will not occur until requested by the host (see steps 45 and 46). Write access is allowed only to a single terminal. When a terminal holding a copy of a shared file receives a file update notification, it sets the corresponding file as invalid on the management table 24. In step 40, if the access request is a read access, the corresponding block of the memory 23 is accessed (step 43), and the access ends (step 44).

When the terminal side disconnects the line, it requests the host to take over the file updated by write access (step 45). The host requests a file transfer and updates the shared file (step 46). The terminal disconnects the line after transferring all updated files.

By performing the above operations, a match between the shared file and the copy of the file on each terminal is maintained at all times, and the number of accesses from the terminal to the host's file through the communication line is reduced, thereby speeding up access. It is possible to improve the performance and line usage efficiency. Furthermore, by performing the above operations using O8 (operating system) built into the host and the terminal, the terminal user does not need to be aware of the existence of a copy of the file in between.

As described in detail, according to the present invention, a table for managing access to files of each terminal is provided in the host computer, and a table for managing copies of shared files and the status of the copies is provided in the terminals. This has the effect of increasing access speed and reducing the amount of data transferred over communication lines, without the terminal user being aware that he or she is accessing a copy on the terminal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2(A),
(B) is a diagram showing each management table in the host and terminal,
FIG. 3 is a flowchart showing the operation of the embodiment of the present invention. Explanation of symbols of main parts 1...Host calculation unit 2...Terminal device 3...Communication line 4.5...Shared file 13.24... ...Management table 23...Memory

Claims (1)

[Claims] A shared file access method in which a plurality of terminal devices access a shared file owned by a host computer via a communication line, and in the host computer, the access status from each terminal device to the shared file is recorded as a certain block of the shared file. A management table is provided for managing each block, and each of the terminal devices is provided with a storage means for storing a copy of a partial block of the shared file, and a management table for managing an update state of the copy of this block for each block. , in response to the access request to the shared file, searches the management table in the own device for a block copy in the storage means in the terminal device that generated this access request, and if the target block copy exists, searches for it. A terminal device that reads or rewrites and updates, updates a corresponding block of the shared file in response to the update of this block copy, and uses a block copy corresponding to the updated block according to a management table in the host computer. A shared file access method characterized in that update notification of the block is sent to the user.