JP2000089996A - Information processor and data base system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information processor capable of inexpensively constructing a more efficient system for allowing respective clients to mutually utilize caching data in a computer system based on a server-client model and a data base system constituted of the information processor. SOLUTION: Each of clients 121 to 12n checks whether required data out of data stored in a data base 15 are stored in caches 161 to 16n built in the other clients or not by referring to cache management information tables 181 to 18n obtained by inquiring all other clients by a broadcast or a multicast. When the required data are chached in any one of clients, a server 11 is inquired to check the updating time information on the data stored in a data management information table 17, and when the contents of the chached data are the latest, the data are downloaded from the client concerned.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information processing apparatus or a database system constituting a computer system of a client server model, and more particularly to a cache sharing type computer system in which data cached in each client is used by another client. The present invention relates to an information processing device or a database system that constitutes the above.

[0002]

2. Description of the Related Art Conventionally, a database system composed of a plurality of computers connected to each other has a server that centrally manages information resources and a client that uses information managed by the server. A client-server model computer system is used. In the client-server model computer system, information resources such as a shared directory and a database can be centrally managed by the server, but troublesome processing such as a user interface is left to the client, so that there is an advantage that a response to input is fast. .

However, in recent years, in such a computer system, there has been a problem that the accessibility of the system is reduced due to the concentration of accesses from each client to the server. One approach to such problems is to use the Internet Engineering Task Force (IETF) in the Internet, which is a worldwide communication network.
RFC (Req) issued by the Internet Engineering Working Group
uest for comments) As described in 2186 and RFC 2187, each WWW is distributed by distributing a cache among a plurality of WWW (World Wide Web) servers.
The main technology was to improve accessibility to servers. However, for example, a corporate LAN (Local Area Net
In a network constructed in a limited area such as an intranet as a local information communication network), not only sharing of load between servers but also sharing of load with clients poses a problem of reduced accessibility. It can be a powerful approach to solving. Hereinafter, this point will be described.

[0004] That is, in the past, in the intranet as an intra-company LAN, the intra-company communication used to be mainly the communication in each department. However, due to the penetration of client-server systems, high-performance and high-performance servers have been concentrated in the core of the network, and communications in which each client accesses servers located outside the department have become internal to the company. It has become the majority of communications.

As described above, when the access from each client to the server outside the department, that is, the access to the core of the network described above, is concentrated, the traffic there becomes excessive, and eventually, each client accesses the network. Sex will be reduced. Therefore, to use the network efficiently,
It is necessary to devise ways to minimize the load on the servers located at the core of the network.

FIG. 5 shows an example of a technique for reducing traffic in a server in a conventional client server system. This technique is disclosed in JP-A-5-274210.

First, when it becomes necessary for the first client 202 to use a data file managed by the server 201, the file control unit 203 first checks whether or not the data file is cached in the cache 204. . If the data file has been cached, the data file is read from the cache 204. If the data file has not been cached, the network OS (Operat
ing System) 205 is requested to access the server 201 via the network 200.

Upon receiving a data file transfer request from the first client 202, the file management unit 206 of the server 201 refers to the file management information 207 to determine whether the data file has already been cached by another client. Confirm. If the data file has not been cached, the server 201 sends the data file to the network OS 208 from the disk device 209 for the first time.
To the client 202. on the other hand,
The data file is, for example, the second client 210
If the cached data is cached to the second client 210, the cached data is transmitted to the first client 210.
To the client 202. Accordingly, each client can improve the network accessibility by receiving the data from another client when the other client is caching the data. Further, it is also possible to reduce the amount of data transmitted via a network by enabling data to be directly transferred from a database to another terminal via one terminal connected to the network.

FIG. 6 shows an example of such a conventional technique disclosed in Japanese Patent Application Laid-Open No. 8-274806. here,
Among the plurality of databases 212 _{1 to} 212 _n accessible via the network 211, each terminal 213 _{1 to} 21 ₁
When it is requested to transmit the data from the 3 _n to another terminal, select the database that the database management system 214 can transmit a most efficient data, to request the transfer of data to the database It has been disclosed.

Japanese Patent Application Laid-Open No. 9-54719 discloses another conventional technique for reducing the amount of data transmission via a network.

FIG. 7 shows the configuration of the prior art. Here, a plurality of clients 221 constituting the database
_1, 221 by creating comprising a ₂ and the server 222 and the equivalent data files 223 ₁ to 223 ₃ respectively, thereby reducing the amount of data transmission over the network. That is, the server 222 and the history 224 that records the time of the data update, the client 221 _1, 221 ₂ is provided with an account 225 records the time when the logging on or off in the database.

The server 222 is connected via a network 226
For example, the first client 221 ₁Is file 223₁
When you know that you have updated the contents of
Updates are recorded and file 223_Twoand
File 223_ThreeFile 223₁Updated as well
I do. Also, for example, the first client 221₁Is the log
When turned off, the logoff time is recorded in the history 224.
It is. First client 221₁Logged on again
Sometimes, referring to the recorded content of the history 224, the first click
Client 221₁File 2 while the user is logged off
23_Two, 223_ThreeCheck that the contents of have not been updated
You. If there is an update, the file is updated according to the update.
Le 223₁Update the contents of However, like this,
The client has the same data file as the server
Each client has a large storage device
Must be managed and the server manages the data files.
The benefits of intensive processing are diminished.
Therefore, the same data is duplicated for all clients
Database for each client instead of storing
The various data of the source to minimize duplication
Then, each client mutually exchanges the stored data
Use each other in a modest manner in the network.
Various techniques for dispersing traffic have been proposed.

FIG. 7 shows an example of such a conventional technique in a host-terminal type computer system. This technique is disclosed in Japanese Patent Application Laid-Open No. Hei 10-11375. That is, the host computer 231 has a document body information file 232 for storing document body information, and a host document management table 233 for managing information on the last update time of the document body information. On the other hand, the workstation 234 has a cache file 2 for storing the document body information received from the host computer 231.
35, and a local document information management table 236 having management information on document body information stored in the cache file 235.

When the workstation 234 receives a request for displaying a document, the local document information management table 236
It is determined whether or not the requested document is stored in the cache file 235 with reference to the information in the above. If not, the document is transferred from the host computer 231 via the network 237. on the other hand,
If the document is stored in the cache file 235, information on the last update time of the document is stored in the host computer 2.
It is passed to 31. The host computer 231 compares the received information on the last update time with the information on the last update time stored in the host document management table 233 to determine whether or not the content of the cached document is the latest content. I do. If so, the workstation 234 is notified to that effect, and the workstation 234 displays the cached document,
This processing ends. If the document cached in the workstation 234 is not the latest document, the latest document is transferred from the host computer 231 to the workstation 234.

FIG. 8 shows a technique disclosed in Japanese Patent Application Laid-Open No. 6-52119. Here, the server 241 and the first
And second clients 242, 243 are connected via a common network 244, 245, and each network 244, 245 is provided with first and second gates 246, 247, respectively. It is connected via a wide area network 248.

In the distributed data processing system having such a configuration, for example, the first client 242
Requests the file 250 stored in the disk device 249, the server 241 permits the first client 242 to create the replica file 251. First
Client 242 creates the replica file 25
1 is stored in the disk device 252.

The second gate 247 monitors the distribution state of the data permitting the creation of the replica file. The replica file 251 of the file 250 is created by the first client 242 and stored in the disk 252. Is recorded in the table 253.

Thereafter, when the second client 243 requests the server 241 to refer to the file 250,
When the second gate 247 recognizes the requested fact, the information in the table 253 is searched. When the reference indicated by the request fact matches the reference indicated by the update fact, the second gate 247 determines the reference destination of the second client 243 and the gate 248 recognizes that the request has been made. , Second
Is changed from the server 241 to the first client 242. Thereby, the second
Will access the replica file 251 instead of the file 250 itself.

[0019]

As described above, conventionally, in a client-server model database system, various techniques for mutually using data cached by each client have been proposed for the purpose of reducing traffic in a server. Have been.

However, in the various conventional techniques described above,
The specific configuration in which each client obtains information about data cached to other clients is not explicitly indicated, or even if indicated, a special switch, for example, a "gate", is provided in the network. Thus, the configuration for monitoring the data caching status of each client has been disadvantageously increased in system construction cost.

Further, in the above-mentioned conventional techniques, caching data is mutually used between clients set in advance. Therefore, an appropriate client that uses caching data mutually can be used. In some cases, there is an inconvenience that caching data cannot be mutually used between such clients.

An object of the present invention is to provide a computer system based on a server-client model, which is capable of constructing, at a low cost, a more efficient system for allowing each client to mutually use caching data, or this information. An object of the present invention is to provide a database system including devices.

[0023]

According to the first aspect of the present invention, (a) first information acquisition means for acquiring information on an update time of each data in the database from a server managing the database; Second information acquisition means for directly inquiring each client about the data of the database currently stored by each client using the database and the update time of the stored data by inquiring each client, and (c) first information With reference to the information acquired by the acquisition unit and the information acquired by the second information acquisition unit, when the data of the database currently stored by any of the clients is the latest, the data is The information processing apparatus is provided with data transmission request means for requesting any client to transmit.

That is, according to the first aspect of the present invention, information on the update time of each data in the database is obtained from the server managing the database, and the data in the database currently stored by each client using the database. Information about the update time of the stored data is directly inquired to each client and acquired. The obtained information is referred to, and when the data of the database currently stored in any of the clients is the latest, the client is requested to transmit the data. Thereby, the data of the database stored by each client can be mutually used without providing a special monitoring device in the system including the server and the client.

According to the second aspect of the present invention, (a) first information acquisition means for acquiring information relating to the update time of each data in the database from a server managing the database, and (b) each client using the database. A second information obtaining means for inquiring each client about the data of the database currently stored therein and information on the update time of the stored data by simultaneous broadcast, and (c) the first information obtaining means. By referring to the acquired information and the information acquired by the second information acquiring means, if any of the clients currently stores the latest data in the database, the data is transmitted. The information processing apparatus is provided with a data transmission request unit that requests any of the clients.

That is, according to the second aspect of the present invention, information on the update time of each data in the database is obtained from the server that manages the database, and the data in the database currently stored by each client using the database. Information on the update time of the stored data is inquired to each client by simultaneous broadcast and acquired. The obtained information is referred to, and when the database data currently stored in any of the clients is the latest data, the client is requested to transmit the data. Thereby, the data of the database stored by each client can be mutually used without providing a special monitoring device in the system including the server and the client.

According to the third aspect of the present invention, (a) first information acquiring means for acquiring information relating to the update time of each data in the database from a server which manages the database; A second information acquisition unit for acquiring information on a history of download of each data of the database by the client; and (c) an identical database from each client using the database based on the information acquired by the second information acquisition unit. (D) Among the clients using the database, the clients that are in the range of normal communication by broadcast and the clients that are selected by the screening means are The stored database data and the stored data A third information obtaining means for directly inquiring and obtaining information on the new time, and (e) referring to information obtained by the first information obtaining means and information obtained by the third information obtaining means, When the data in the database currently stored by any one of the clients in the range of normal communication by the broadcast and the client selected by the selection means is the latest one, a request is made to any client to transmit the data. And a data transmission requesting means.

That is, according to the third aspect of the present invention, information on the update time of each data in the database is obtained from the server managing the database, and each client using the database downloads each data in the database. Information about the history is obtained. Clients that have a high possibility of using the same data in the database are selected from each client that uses the database based on information on the history of each client downloading each data in the database. Among the clients that use the database, the clients in the range that normally communicates by broadcast and the selected clients are directly inquired about the database data currently stored and the information on the update time of the stored data and obtained. Is done. With reference to the information obtained by the first information obtaining means and the information obtained by the third information obtaining means, any one of the clients within the range of normal communication by broadcast and the selected clients is currently stored. If the data in the database being updated is the latest, the client is requested to transmit the data. As a result, the data of the database stored between clients that are likely to use the same data can be mutually used beyond the range of clients that normally communicate by broadcast.

According to the present invention, (A) database management means for managing the database, and updating of each data in the database in response to an inquiry from each client using the database managed by the database management means. A server having notification means for notifying information on time, (b) first information obtaining means for obtaining information on update time of each data of the database from this server, and each client using the database currently storing Second information acquisition means for directly inquiring each client about information on the data of the database being updated and the update time of each stored data, and information acquired by the first information acquisition means and second information Each client with reference to the information obtained by the information obtaining means of Any data in the database that are currently stored in the case is current, constituting a database system and a client and a data transmission request means for requesting the one of the clients to send the data.

That is, in the invention according to claim 4, the server that manages the database notifies information about the update time of each data of the database in response to an inquiry from each client that uses the database. Correspondingly, each client obtains information on the update time of each data of the database from the server, and each client using the database obtains information of the database data currently stored and the update time of the stored data. To get information about each client directly. The obtained information is referred to, and when the data of the database currently stored in any of the clients is the latest, the client is requested to transmit the data. As a result, the data of the database stored by each client can be mutually used without providing a special monitoring device in the database system.

According to the fifth aspect of the present invention, (a) database management means for managing the database, and update time of each data of the database in response to an inquiry from each client using the database managed by the database management means (B) first information acquisition means for acquiring information on the update time of each data in the database from this server, and each client using the database currently stores the information. A second information acquisition unit for inquiring each client about the data of the stored database and the update time of each of the stored data by simultaneous broadcast, and information acquired by the first information acquisition unit. 2 with reference to the information obtained by the information obtaining means A data transmission requesting means for requesting any one of the clients to transmit the data when one of the data stored in the database is the latest data. .

That is, in the invention according to claim 5, the server that manages the database notifies information on the update time of each data in the database in response to an inquiry from each client that uses the database. Correspondingly, each client obtains information on the update time of each data of the database from the server, and each client using the database obtains information of the database data currently stored and the update time of the stored data. Inquires and obtains information about each client by broadcast. The obtained information is referred to, and when the data of the database currently stored in any of the clients is the latest, the client is requested to transmit the data. As a result, the data of the database stored by each client can be mutually used without providing a special monitoring device in the database system.

According to the invention described in claim 6, (a) database management means for managing the database and each data of the database in response to an inquiry from each client using the database managed by the database management means. A server having notification means for notifying information on the update time and information on the history of each client downloading each data in the database; and (b) acquiring information on the update time of each data in the database from the server. First information acquiring means, second information acquiring means for acquiring information on a history of each client using the database downloading each data in the database, and a database based on the information acquired by the second information acquiring means. From each client that uses And selection means for possibility to use the same data database is selected a high client,
Among the clients that use the database, the clients in the range that normally communicates by broadcast and the clients that are selected by the selection unit are directly provided with the data of the currently stored database and the information on the update time of the stored data. A third information acquisition unit that obtains an inquiry and an information that is obtained by the first information acquisition unit and the information that is acquired by the third information acquisition unit. When the data of the database currently stored by any of the client and the client selected by the selection unit is the latest data, the database system is configured to transmit the data with the client.

That is, in the invention according to claim 6, the server that manages the database, in response to an inquiry from each client that uses the database, updates the information on the update time of each data in the database and the client updates each data in the database. Notify information about download history. Correspondingly, each client obtains information about the update time of each data in the database from the server and information about the history of each client downloading each data in the database, and each client using the database stores the information at present. The data of the stored database and the information on the update time of the stored data are inquired to each client by simultaneous broadcast and acquired. The obtained information is referred to, and when the data of the database currently stored in any of the clients is the latest, the client is requested to transmit the data. As a result, a database system capable of mutually using database data stored between clients that are likely to use the same data and that exceed the range of clients that normally communicate by simultaneous broadcast Can be constructed.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments.

FIG. 1 shows a computer system having an information processing apparatus according to one embodiment of the present invention. This computer system is, for example, a corporate LAN (Local Area N).
etwork; a client-server type database system installed on an intranet as a private information communication network), and is composed of a plurality of information processing apparatuses interconnected via a network. That is, a server 11 for searching and managing a database is provided at the center of the system, and _first to _n-th clients 121 to 12n using a database 15 managed by the server 11 connect to the network 10. Connected to each other.

The server 11 is a database server software 1
The database server software 13 searches and manages the database 15. Also,
The server 11 has a database management information table 17 for recording information on the update time of data stored in the database 15 and the like.

Each client 12₁~ 12_nAre each
Database client software 14 ₁~ 14_nAnd
Cush 16₁~ 16_nIt has. Each client 12
₁~ 12_nIs database client software 1
4₁~ 14_nAllows users to display screens and print data.
Performs processing related to the interface and data
Temporarily caches data stored in the base 15
6₁~ 16_n(Hereinafter, data is stored in the cache
(Remembering is also called caching.)
Run. The database client software 14₁
~ 14_nIs for each client 12₁~ 12_nAre each
Cache 16₁~ 16_nData stored in
Perform various processes to build a shared cache relationship
Run.

FIG. 2 shows a cache management information table stored for each client to use the caching data with another client. The cache management information tables 18 ₁ to 18 _n store “server address”, “information ID (IDentification)”, “information ID (IDentification)” for each cached unit of data (hereinafter, this unit of data is referred to as a data file). Information of each item of “acquisition time” and “pointer” is recorded.

The "server address" is information indicating a server that manages a database including the data file. Specifically, a protocol address of the server or a host name in the network, or a hash code calculated from the protocol address or the host name is used. "Information ID (IDentificatio
“n)” is information indicating the data file itself. Specifically, file names on the server and http (HyperText Tr
ansfer Protocol (Hypertext Transfer Protocol)
An address represented by a URL (Uniform Resource Locator) and a hash code calculated from the file name and the address represented by the URL are used.
“Acquisition time” is information indicating the time at which the data file was cached by any client.
The “pointer” is information indicating a client in which the data file is cached. Specifically, a protocol address of the client or a host name in the network, or a hash code calculated from the protocol address or the host name is used. These cache management information tables 18 ₁ to 1
The contents of each piece of information constituting 8 _n are described in each of the clients 12 ₁ to 1.
Rewritten according to the cache management message communicated between 2 _n .

FIG. 3 shows a data structure of a cache management message communicated between each client. The type of the cache management message is identified by the control code. That is, the types of cache management messages identified by the control code include “cache inquiry”, “cache information request”, “cache hit”, and “cache miss”.

The "Cache Query" is a message for inquiring whether desired data files between the client 12 ₁ to 12 _n is cached on other clients. "Cache information request"
This message requests that data cached by another client be transferred to that client. "Cache hit" is for each client 1
This message notifies other clients that 21 _{1 to} 12 _n are caching a certain data file. The “cache miss” indicates that each client 12 ₁ to 1
_2n is a message notifying another client that no data file has been cached. These various messages identified by the control code all include information of items of “request source address”, “response source address”, “server address”, “request information ID”, and “acquisition time”.

The "request source address" is information indicating a client that requires the data file. Specifically, a protocol address of the client or a host name in the network, or a hash code calculated from the protocol address or the host name is used. “Response source address” is information indicating a client caching the data file. Specifically, a protocol address of the client or a host name in the network, or a hash code calculated from the protocol address or the host name is used. “Server address” is information indicating a server that manages the data file. Specifically, a protocol address of the server or a host name in the network, or a hash code calculated from the protocol address or the host name is used. “Request information ID” is information indicating the data file itself. Specifically, a file name on the server, an address represented by a URL in http, and a hash code calculated from the file name and the address represented by the URL are used. The “acquisition time” indicates that the data file is one of the clients 1
This is information indicating the last time at which it was confirmed that it was at 2 _{1 to} 12 _n .

Next, the first client 12 ₁ is an example in which requests data file 14 by the server 11 is managed, the operation of the information processing apparatus of this embodiment.

FIG. 4 shows the flow of processing in this case.

Firstly, if necessary first client 12 ₁ to use the data file 14 managed by the server 11 occurs, the first client 12 ₁ is the last of the data file 14 to the server 11 via the network 10 An update time is inquired (step S101). Server 1
1 is a data file 1 from the data management information table 17
4 reads out the information about the time at which the contents of the first client 1 were last updated, and sends the first client 1 via the network 10.
To notify the 2 _1.

After the first client 12 ₁ obtains information on the last update time of the data file 14, the first client 12 ₁ refers to the information recorded in the cache management information table 18 ₁ and selects one of the clients 12 _{1 to} 12 _n. whether the data file 14 is cached, i.e. information "information ID" indicates the data file 14 is checked or not registered in the cache management information table ₁₈₁ (step S102).

[0048] If the data file 14 is registered in the cache management information table 18 _1, the "pointer"
See, first checks whether the data file 14 has not been cached in the first client 12 ₁ itself (step S103). If it is cached in the first client 12 ₁ itself, in contrast and information about the last update time of the inquiry to the time information and the server 11 indicated by the "acquisition time", the contents of the data file 14, which is caching the latest Is checked (step S104). That is, when the time indicated by the "acquisition time" is later than the last update time of the inquiry to the server 11 determines that the contents of the data file 14 that is cached is up-to-date, the data from the cache 16 ₁ Read (step S105).

At the same time, the first client 12 ₁
Sends a "cache hit" message to cause each client to update the cache management information (step S106). In other words, "information ID" indicates the data file 14, "request source address" and indicates the client 12 ₁ each item first the "response source address", "acquisition time" is the current time "cache hit" To all other clients by broadcast or multicast.

The other clients receiving the "cache hit" message update the contents of the respective cache management information tables 18 ₂ to 18 _n in accordance with the received "cache hit" message. That is, if information on the data file 14 has already been registered in the cache management information table, the “acquisition time”
Is updated to match the "acquisition time" of the "cache hit" message. Also, information about the data file 14 is not registered in the cache management information table, the "Server Address" and the server 11, the "information ID" as data file 14, a first client 12 ₁ to "pointer", The “acquisition time” is matched with the “acquisition time” of the “cache hit” message and registered in the cache management information table.

[0051] In step S103, if if "pointer" indicates the other clients, for example, the second client 12 ₂ is caching the data file 14 refers to the "acquisition time", the data It is checked whether the content of the file 14 is the latest one (step S107). If the latest one, sends a message of "cache information request" second to the client 12 ₂ (step S108).

This "cache information request" message
, The second client 12 _TwoFrom data file
14 and "cache hit" message
If the message has been taken (step S109; Yes),
Cache management information table 18 according to the content of the message
₁Is updated (step S110), and this processing ends.
That is, the second client 12_TwoIs the first client
12₁From "cache information request" message
Upon receipt, data file 14 is actually
6_TwoTo see if it has been cached. Cashin
If the data file 14 has been
Iant 12₁To the cache hit
Message to the first client.
Iant 12 ₁And the "response source address"
Iant 12_TwoAs broadcast or multi
Sent to all other clients by casting. This
All "cache hit" messages received
According to the content of this message, the client
Each time, the contents of the cache management information table are updated.

[0053] On the other hand, the message of the case that has not been the second data file 14 to the client 12 ₂ is actually caching when receiving a message of "cache information request" from the first client 12 _1, a "cache miss" To all other clients by broadcast or multicast. All clients that have received the "cache miss" message delete the registration information of the data file 14 from each cache management information table.

Further, the first client 12 ₁ has the second client 12 ₁
Upon reception of the message "cache miss" from the client 12 _2, and deletes the registration information of the same data file 14 and other clients (step S11
2), together with the server 11, the data file 14
Is requested (step S113). The first client 12 ₁ receives the transfer of the data file 14 from the server 11, caching data file 14 which is the transfer to the cache 16 ₁ (step S11
With 4) transmits "request source address" and by broadcast or multicast a message to "response source address" client 12 ₁ together first the "cache hit" to all other clients (step S115), the The process ends.

[0055] In addition, each client and the first client 12 _1, which has received the message of "cache hit" from the first client 12 _1, the "server machine address" as a server 11, "information ID" of the data file 14 and then, the "pointer" to the first client 12 _1, "acquisition time" the first client 12 ₁ is information for the time that received the transfer of the data file 14 from the server 11 of each cache management information table 1
Register at 8 ₁ to 18 _n .

[0056] If the data file 14 in the cache management information table ₁₈₁ is not registered in step S102, the first client 12 ₁ sends a message "cache query" to another client for confirmation (step S116). When a "cache hit" message is received from any client in response to this message (step S11).
7; Yes), it is checked whether the cache data has the latest contents (step S118). If it is the latest content, "Request cache information" to the client
Is transmitted (step S119), and the process ends. Further, when the message of “cache hit” is not received (step S117; No), and when the message is not the latest information (step S118;
No) shifts to the processing after step S113 described above. Also, when it is determined in step S104 and S107 that the information is not the latest information, similarly, in step S1
The processing shifts to the processing after step 13.

Next, a description will be given of a process in the case where each client temporarily leaves the above-mentioned data sharing system or joins this data sharing system again.

For example, when the first client 12 ₁ intentionally leaves the data sharing system, the first client 12 ₁ relates to the data whose “pointer” is itself in the cache management information table 18 ₁ by “ A "cache miss" message is broadcast or multicast to all other clients. That is, the client that has received the “cache miss” message deletes the registration information of the data file 14 of the cache management information.

Further, the client itself leaving the data sharing system can leave the system without performing any special processing. For example, IEEE (Instit
uteof Electrical and Electronics Engineers (Ethernet) conforming to 802.2 and IEEE 802.3, and ATM-U
NI (Asynchronous transfer mode-User Network In
terface; Asynchronous transfer mode—user / network interface) In a network system based on the 3.1 system, a line disconnection is detected when a client logs off. to remove the registration information of the file from the cache management information table 18 ₁ ~18 _n.

If a client stops responding to the message related to the cache management information, it may be determined that the client has left the system when the state continues for a predetermined time. In this case, the client that first recognizes the departure of all the clients transmits a “cache miss” message to all the other clients by broadcast or multicast with respect to the data file.

In the above-described embodiment, the range of the clients sharing the cache is set to the clients that exchange communications by multicast or broadcast. However, the present invention is not limited to this. For example, server 1
1 Record the client download each data file in the database 15 from the message of "cache hit" received from the client 12 ₁ to 12 _n, the last update of the data file from the client 12 ₁ to 12 _n Inquiry of time (step S1
01), the client is notified of the client that downloaded the data file.
The client that has received the notification adds the client that has downloaded the data file to the range of clients that communicate the cache management message by multicast. This makes it possible to automatically add, to the cache sharing relationship, a client that has a high possibility of downloading the same data file as the data file used by the client. For this reason, clients that are likely to be caching necessary data files beyond the range of clients that normally communicate by broadcast are added to the range of clients that communicate cache management messages, and a more effective cache sharing relationship. Can be easily constructed.

[0062]

According to the first aspect of the present invention, information on the update time of each data in the database is obtained from the server managing the database, and the database currently stored in each client using the database. Is directly inquired to each client and information on the update time of the stored data is obtained. The obtained information is referred to, and when the data of the database currently stored in any of the clients is the latest, the client is requested to transmit the data. Thereby, the data of the database stored by each client can be mutually used without providing a special monitoring device in the system including the server and the client. Therefore, it is possible to construct at low cost a system that can prevent a decrease in the accessibility of the database system due to excessive traffic in the server.

According to the second aspect of the present invention, information on the update time of each data in the database is obtained from the server managing the database, and the data in the database currently stored by each client using the database. Information on the update time of the stored data is inquired to each client by simultaneous broadcast and acquired. The obtained information is referred to, and when the database data currently stored in any of the clients is the latest data, the client is requested to transmit the data. Thereby, the data of the database stored by each client can be mutually used without providing a special monitoring device in the system including the server and the client. Therefore, it is possible to construct at low cost a system that can prevent a decrease in the accessibility of the database system due to excessive traffic in the server.

That is, according to the third aspect of the present invention,
From the server that manages the database, information on the update time of each data in the database is obtained, and information on the history of downloading each data in the database by each client using the database is obtained. Clients that have a high possibility of using the same data in the database are selected from each client that uses the database based on information on the history of each client downloading each data in the database. Of each client that uses the database,
Broadcasting directly inquires and retrieves the data of the database currently stored and the information on the update time of the stored data from the clients in the range of normal communication and the selected clients. The information obtained by the first information obtaining means and the information obtained by the third information obtaining means are referred to, and one of the clients in the range of normal communication by broadcast and the selected clients is currently stored. If the data in the database being updated is the latest, the client is requested to transmit the data. As a result, the data of the database stored between clients that are likely to use the same data can be mutually used beyond the range of clients that normally communicate by broadcast. Therefore, a more effective system that can prevent a decrease in the accessibility of the database system due to excessive traffic in the server can be easily constructed at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an outline of a database system including an information processing device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an information configuration of a cache management information table used in the embodiment.

FIG. 3 is a table showing an information structure of a cache management message used in the embodiment.

FIG. 4 is a flowchart illustrating an operation of the information processing apparatus according to the present exemplary embodiment.

FIG. 5 is a flowchart illustrating an operation of the information processing apparatus according to the present exemplary embodiment.

FIG. 6 is a flowchart illustrating an operation of the information processing apparatus according to the present exemplary embodiment.

FIG. 7 is a block diagram showing an outline of a conventional database system.

FIG. 8 is a block diagram showing an outline of a conventional database system.

FIG. 9 is a block diagram showing an outline of a conventional database system.

FIG. 10 is a block diagram showing an outline of a conventional database system.

FIG. 11 is a block diagram showing an outline of a conventional database system.

[Explanation of symbols]

11 server 12 _{1 to} 12 _n client 13 database server software 14 _{1 to} 14 _n database client software 15 database 16 _{1 to} 16 _n cache 17 data management information table 18 ₁ to 18 _n cache management information table

Claims (6)

[Claims] A first information acquisition unit for acquiring information on an update time of each data of the database from a server managing the database; and a data of the database currently stored by each client using the database. Second information obtaining means for directly inquiring each client about information on the update time of the stored data, information obtained by the first information obtaining means, and information obtained by the second information obtaining means Information and
Data transmission request means for requesting any one of the clients to transmit the data when the data of the database currently stored by any of the clients is the latest data. Information processing device. 2. A first information acquisition means for acquiring information on an update time of each data of the database from a server which manages the database; and data of the database currently stored by each client using the database. Second information acquisition means for inquiring the client about the update time of the stored data by simultaneous broadcast to the clients, and acquiring the information acquired by the first information acquisition means and the second information acquisition With reference to the information obtained by the means,
Data transmission request means for requesting any one of the clients to transmit the data when the data of the database currently stored by any of the clients is the latest data. Information processing device. 3. A first information acquiring means for acquiring information on an update time of each data of the database from a server which manages the database, and a history that each client using the database downloads each data of the database. A second information acquisition unit for acquiring information about the client, and a client that is highly likely to use the same data in the database from each client that uses the database based on the information acquired by the second information acquisition unit Selecting means for selecting, and among the clients using the database, the data of the database currently stored in the clients in the range of normal communication by simultaneous broadcast and the clients selected by the selecting means, and the storage of the data Update time of the A third information acquisition unit that directly inquires and acquires information that is obtained by referring to information acquired by the first information acquisition unit and information acquired by the third information acquisition unit.
When the data of the database currently stored by any one of the clients in the range of normal communication by the broadcast and the client selected by the selection unit is the latest data, the client transmits the data. And a data transmission requesting means for requesting the client. 4. A database management unit for managing a database, and a notifying unit for notifying information on an update time of each data of the database in response to an inquiry from each client using the database managed by the database management unit. A first information acquisition unit for acquiring information on an update time of each data of the database from the server; and data of the database currently stored by each client using the database; and Second information obtaining means for directly inquiring each client about information on the update time of each stored data, information obtained by the first information obtaining means, and information obtained by the second information obtaining means Refer to the information and A data transmission requesting means for requesting any one of the clients to transmit the data when the data of the database currently stored is the latest data. Characteristic database system. 5. A database managing means for managing a database, and a notifying means for notifying information on an update time of each data in the database in response to an inquiry from each client using the database managed by the database managing means. A first information acquisition unit for acquiring information on an update time of each data of the database from the server; and data of the database currently stored by each client using the database; and Second information acquisition means for inquiring the client about the update time of each stored data by simultaneous broadcast to each client, and acquiring the information acquired by the first information acquisition means and the second information acquisition By referring to the information obtained by the A data transmission requesting means for requesting any one of the clients to transmit the data when the data of the database currently stored by any of the clients is the latest data. A database system, characterized in that: 6. A database management unit that manages a database, and in response to an inquiry from each client that uses the database managed by the database management unit, information about an update time of each data in the database and each client A server having notification means for notifying information on a history of downloading each data of the database; first information obtaining means for obtaining information on an update time of each data of the database from the server; and the database Information acquisition means for acquiring information on a history of each client using the database to download each data of the database, and each client using the database based on the information acquired by the second information acquisition means From the Selection means for selecting a client having a high possibility of using the same data of the database, and among clients using the database, a client in a range which normally communicates by broadcast and a client selected by the selection means A third information obtaining means for directly inquiring and obtaining information on the data of the database currently stored and an update time of the stored data; information obtained by the first information obtaining means; 3 with reference to the information obtained by the information obtaining means, the data in the database currently stored by any one of the clients in the range of normal communication by the broadcast and the clients selected by the selection means If it is up-to-date, any of the above A database system comprising: a client having data transmission request means for requesting a client.