JP2003177951A - Database sharing system, its buffer discarding method, and its processing program - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a database sharing system for efficiently using and discarding buffer data in a database sharing system performing exclusive control. SOLUTION: In a database sharing system 10 according to the present invention, an exclusive control device 130 includes a host computer 1
00 and a data flag in the database storage device 170, a first flag indicating that the data resource stored in the buffer is discarded, and a second flag indicating that this data resource is not discarded. And a flag notification for notifying which one of the first and second flags is recorded in the corresponding cell when the corresponding list is detected based on the update / reference request. The second flag is recorded for the corresponding cell in the buffer discarding table 150 by the unit 142 and the other host computer 100
And a flag setting unit 144 for recording a first flag for a cell corresponding to the data resource.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for managing data stored in a buffer in a database sharing system using an exclusive control device, and more particularly, to efficiently use data resources in the buffer of an information processing device read from a database. The present invention relates to a database sharing system for effectively using and discarding, a buffer discarding method thereof, and a processing program thereof.

[0002]

2. Description of the Related Art With respect to a database shared by a plurality of information processing apparatuses, for example, a host computer, setting / releasing processing of exclusive control in an exclusive control apparatus is accompanied by reference / update processing, and with a host computer. It is necessary to read / write data from / to the storage device of the database. At this time, the desired data resource in the database is written page by page in the main memory of the host computer or the buffer for virtual memory.

A technique for improving the processing efficiency and speeding up the entire system by effectively using the data written in this buffer is disclosed in Japanese Patent Laid-Open No. 10-91510 (hereinafter,
Reference 1).

In this document 1, a file exclusion controller that performs exclusive control between computers manages the generation number of a local buffer, and notifies the lock request source system of the generation number as return information of a lock request at the time of file access. To do. In this lock request source system, the notified generation number is compared with the generation number of the local buffer managed in the local host computer, and if they match, the file in the local buffer is used and there is a mismatch. In this case, the file in the local buffer is discarded and the desired file is newly read from the database.

Further, in Japanese Patent Laid-Open No. 5-73394 (hereinafter referred to as Document 2) described in Document 1, the following processing is performed in a loosely coupled system including a plurality of host computers. The host computer that accesses the shared file acquires the access right (exclusion right) to the shared file by setting the exclusion control flag in the shared memory (step S1). The shared memory is accessed again, the shared file update flag in the shared memory is referenced, and it is determined whether the flag corresponding to the host computer is set (step S).
2). If the flag is set as a result of the reference, it indicates that the shared file has been updated from another host computer. As a result, the data of the shared file is read back into the local buffer in the host computer, the shared memory is accessed again, and the shared file update flag for the host computer is reset (step S3). If the flag corresponding to the host computer is not set in the shared file update flag in the shared memory, the data in the local buffer of the host computer is used (step S4).

[0006]

However, in the above-mentioned document 1, the generation number of a file accessed once is shared even if the local buffers of all the shared host computers are discarded. The entire system needs to be retained unless stopped. Therefore, as the amount of data stored in the database increases, the generation number management information increases as the database management unit changes from file units to access site (page) units (that is, the lock granularity is smaller). Becomes a huge amount of data in the shared memory. This may lead to a processing delay in the generation management processing and eventually to a reduction in the performance of the entire database sharing system.

Further, in the above-mentioned document 2, the exclusive control means controls access to the exclusive control flag on the shared memory,
The access to the shared file update flag is performed using the update detection means, but if it is applied to a loosely coupled computer system that does not have a shared memory that performs exclusive control, the following communication will be performed. Be understood.

The exclusive control means sends a control signal for locking for file access to the shared memory control program (step S11). The update detection means transmits a control signal for referring to the shared file update flag to the shared memory control program (step S1).
2). If the shared file update flag is read again,
After the data in the shared file is reread into the memory of the host computer by the update detection means, a control signal for resetting the flag corresponding to the host computer in the shared file update flag is set again to the shared memory control program. (Step S13).

In this case, mutual communication occurs twice without re-reading and three times with re-reading. Therefore, in a loosely coupled computer system that frequently accesses a shared file, there arises a problem that the load of communication processing is increased.

The present invention has been made in view of the above problems, and an object thereof is to efficiently use data in a buffer of a host computer read from a database in buffer management of a database sharing system using an exclusive control device. It is to provide a database sharing system to be used / discarded, its buffer discarding method, and its processing program.

[0011]

(1) In order to achieve the above object, a database sharing system according to the present invention comprises:
A database storage device that stores a data resource shared by a plurality of information processing devices having a buffer, and an exclusive control device that performs access exclusive control for an access request to a desired data resource from the information processing device. In the database sharing system, the exclusive control device indicates that the data resource stored in the buffer is discarded in the list corresponding to each of the information processing device and each of the data resources in the database storage device. A buffer discard table that stores a flag (ON) and a second flag (OFF) that indicates that the data resource is not discarded, and a corresponding request based on an update request from the information processing device for the data resource of the database storage device If the list is detected, it corresponds to the information processing device and the data resource in the buffer discard table. Referring to that cell, the first and second flags (ON, OFF) notification of the either is recorded, also, if the corresponding list is not detected,
A flag notification unit that notifies the information processing apparatus of a notification corresponding to the second flag (OFF),
When the notification regarding the first flag (ON) is received, if the data resource is stored, it has buffer discarding means for discarding it, and the exclusive control device further includes a database storage device of the information processing device. The second flag (OFF) is recorded in the cell corresponding to the information processing device and the data resource in the buffer discard table based on the update process for the data resource of It is characterized in that it has a flag setting means for recording the first flag (ON) for the cell corresponding to the resource.

(2) Further, the database sharing system according to the present invention stores a data resource shared by a plurality of information processing devices having a buffer and a desired data resource from the information processing device. In a database sharing system having an exclusive control device that performs exclusive access control for an access request,
The exclusive control device stores in the list corresponding to each of the information processing device and each of the data resources in the database storage device,
From a buffer discard table storing a first flag (ON) indicating discarding the data resource stored in the buffer and a second flag (OFF) indicating not discarding the data resource, and an information processing device. When a corresponding list is detected based on the reference request for the predetermined data resource of the database storage device, the cell corresponding to the information processing device and the data resource in the buffer discard table is referred to Flag notifying means for notifying the information processing apparatus of which flag (ON or OFF) is recorded, and if the corresponding list is not detected, a notification corresponding to the second flag (OFF). When the information processing apparatus receives the notification regarding the first flag (ON), the information processing apparatus discards the data resource, if stored, and a buffer discarding unit. It has exclusive control device further,
If the information processing apparatus detects a corresponding list from the buffer discard table based on the reference processing for the data resource of the database storage device, the second cell is set to the cell corresponding to the information processing apparatus and the data resource in the list. It is characterized by having a flag setting means for recording a flag (OFF).

(3) Further, in the database sharing system of the above (2) of the present invention, the exclusive control device further has all the cells of the list with the second flag (OFF) after the recording by the flag setting means. If there is, it is characterized by having a list deleting means for deleting this list.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to FIGS. FIG. 1 is a block diagram for explaining an example of the overall configuration of a database sharing system according to the present invention. FIG. 2 is a flow chart for explaining the operation at the time of the data update processing of the database sharing system of FIG. FIG. 3 is a block diagram illustrating a part of the branching process along with the flowchart of FIG. 2 (No. 1). FIG. 4 is a block diagram illustrating the operation of part of the branch processing together with the flowchart of FIG. 2 (No. 2). FIG. 5 is a flow chart for explaining the operation at the time of data reference processing of the database sharing system of FIG. FIG. 6 is a block diagram illustrating a part of the operation of the branch processing together with the flowchart of FIG. 5 (No. 1). FIG. 7 is a block diagram illustrating a part of the operation of the branch processing together with the flowchart of FIG. 5 (No. 2). FIG. 8 is a block diagram illustrating a part of the operation of the branch process together with the flowchart of FIG. 5 (No. 3).

(Description of Configuration of Database Sharing System)
First, the overall configuration of the database sharing system according to the present invention will be described with reference to FIG.

The database sharing system 10 comprises a host computer 100, an exclusive control device 130, and a database storage device 170. When used for individual devices and processing units,
After the hyphen "-", 1 to N (N is a natural number of 2 or more) is used to distinguish and represent the host computers 100-1 to 100-N. These devices are connected to each other via communication interfaces 102, 132, 172 by communication lines 10, 12 such as a dedicated line, LAN or packet network.

In the database storage device 170, the shared database 174 stores data shared by the host computers 100.

The host computer 100 has a main storage unit 1.
04, buffer 106, and buffer discard processing unit 11
It is configured with 0. An online terminal device is connected to each of the host computers 100 for use (not particularly shown).

The main memory 104 is a RAM (Random Acces
s Memory), and temporarily stores the data read from the shared database 174. The buffer 102 is a virtual storage unit for supplementing the storage capacity of the main storage unit 104, and stores data in page units. The buffer discard processing unit 110 discards the corresponding data in the buffer 102 based on the buffer discard instruction from the exclusive control device 130 described later.

The exclusive control device 130 includes an exclusive control unit 13
4, a buffer discard table 150, and a buffer discard table processing unit 140. Exclusive control unit 1
34 receives from the host computer 100 an access request for reference / update to a desired data resource in the shared database 174, and while matching the data,
Exclusive control for giving access permission to one or more host computers 100 is performed. The access request includes a reference request for data reference and an update request for data change / deletion to the shared database 174. The exclusive control device 130 permits access from a plurality of host computers 100 based on a reference request (hereinafter referred to as shared lock), and permits access from a single host computer based on an update request (hereinafter referred to as exclusive lock). Called lock).

The buffer discard table 150 comprises a table having a list corresponding to each host computer 100 and each data resource in the shared database 174. A first flag (ON) indicating that the data resource stored in the buffer 106 of the host computer 100 is discarded in each cell in this list.
And a second flag (OFF) indicating that this data resource is not discarded. The buffer discard table 150 is, for example, a table as shown in FIG. 3 described later. The first and second flags are appropriately changed by the buffer discard table processing unit 140 described later each time the reference / update processing is performed.

The buffer discard table processing section 140 has a flag notification section 142, a flag setting section 144, and a list deletion section 146.

The flag notifying unit 142 selects the desired host computer 10 in the buffer discard table 150 based on the update / reference request from the host computer 100 for the desired data resource in the shared database 174.
Search for a list corresponding to 0 and the data resource. Further, if this list is detected, the corresponding cell in the list is referred to, and the first and second flags (ON
Or OFF) is searched for. The flag notification unit 142 occupies this search result
Along with the notification of acquisition of the shared lock, the host computer 100 that issued the update / reference request is notified. In addition, the flag notification unit 142 also outputs the second flag (O) even when the corresponding list is not detected in the buffer discard table 150.
The host computer 100 that issued the update / reference request is notified of information equivalent to FF).

After the update / reference processing for the desired data resource of the shared database 174 of the host computer 100 is performed, the flag setting unit 144 sets the corresponding cell in the buffer discard table 150 to the corresponding cell.
Change processing of the first and second flags (ON, OFF) is performed.
In the case of update processing, the second flag (OF
F) is recorded, and at the same time, the first flag (ON) is recorded for the other cells in the list. In the case of reference processing, the second flag (OFF) is recorded in the corresponding cell.

The list deleting unit 146 is a flag setting unit 14
After the flag changing process in 4, if all the cells of the corresponding list have the second flag (OFF), this list is deleted.

When the host computer 100 receives the notification of the first flag (ON) from the exclusive control device 130, if the corresponding data resource is stored, it discards the buffer discard processing section 110. Have.

Next, the operation of the database sharing system 10 according to the present invention will be described. It should be noted that, here, the update process will be described first, and then the reference process will be described.

(Regarding Update Process) Here, the shared database 174 is requested by an update request from the host computer 100-1 with reference to the flowchart of FIG. 2 and FIGS. Update processing for updating the data A of the record R1 to the data B will be described.

The exclusive control device 130 sends the record R1 which is the desired update target from the host computer 100-1.
The update request for the data resource “page P1” including is received (step S201).

The exclusive control unit 134 that has received this update request
Synchronizes with the exclusive lock control for updating,
The flag notification unit 142 is instructed to refer to the buffer discard table 150. The flag notification unit 142 searches the buffer discard table 150 for a list corresponding to page P1 (step S202). If the corresponding list is not found, the exclusive lock is acquired and the second
A notification corresponding to the flag (OFF) of is sent to the host computer 100-1 that issued the update request (step S2
21). The state of the buffer discard table 150 in FIG.
This shows the case where the corresponding list does not exist.

If the corresponding list is detected in step S202, the "resource" page P of the list is detected.
1 and the "device" referring to the cell corresponding to the host computer 100-1, the first and second flags (ON, OF
It is referred to which state of F) (step S).
203). Here, if the first flag state (ON), a request for a signal notifying that the target data resource needs to be discarded from the buffer together with the notification that the exclusive lock has been acquired is requested. It is transmitted to the original host computer 100-1 (step S204). Also, if the second flag state (OFF), the request source sends a signal notifying that the target data resource does not need to be discarded from the buffer together with the notification that the exclusive lock has been acquired. Host computer 100-
1 (step S211).

The host computer 100 which has received the "buffer discarding required" notification signal in step S204-
In step 1, the buffer discard processing unit 110-1 discards the page P1 which is the corresponding data resource in the buffer 106-1 (step S205). The host computer 100-1, which has received the “buffer discarding rejection” notification signal in step S211, can refer to the data by using the page P1 already stored in the buffer 106-1. If the corresponding list in step S221 does not exist, the host computer 100-
In No. 1, since there is no record of being read into the buffer 106-1 or only the reference processing described later is performed, the buffer discard processing is not performed in this case.

The host computer 10 by the user
Record R of the shared database 174 via 0-1
The data A of No. 1 is updated to the data B, and the update process ends (steps S206, S212, S222).

Steps S206, S212, S22
With the completion of the updating process of No. 2, the exclusive control device 130 is notified of the exclusive lock release request. Step S20
6, in S212, the flag setting unit 144
In the corresponding list in the buffer discard table 150, the corresponding cell is changed to the second flag (OFF) and all other cells are changed to the first flag (ON) (steps S207 and S213). In step S222, the flag setting unit 144 newly adds a corresponding list in the buffer discard table 150, sets the corresponding cell in this list to the second flag (OFF), and sets all other cells. Is changed to the first flag (ON) (step S223). The buffer discard list 150 of FIG. 4 illustrates the state of step S223. Here, a list corresponding to page P1 is newly added. Then, the second flag (OFF) is set in the cells corresponding to the updated host computer 100-1 and page P1.
However, the first flag (ON) is recorded in the other cells of the list.

After that, the exclusive lock in the data resource requested to be updated is released, and a notification to the effect that this has been released is sent to the requesting computer 100-1 (step S231).

As described above, according to the update processing, the data in page units stored in the buffer of each host computer is appropriately matched in synchronization with the update control, so that the host read from the database is read. A database that can efficiently use the data in the computer's buffer and reduce the communication with the database storage device for reading the data, and can appropriately discard the page resources accumulated in the buffer. A shared system can be realized.

(Regarding Reference Processing) Next, referring to the flowchart of FIG. 5 and FIGS. 6 to 8 showing the branched part of the processing, a reference request from the host computer 100-2 is issued to the shared database 174. Record R
The reference process of referring to 1 will be described.

The exclusive control device 130 receives from the host computer 100-2 the record R1 which is the desired update target.
The reference request for the data resource “page P1” including “” is accepted (step S501).

The exclusive control unit 134 that has received this reference request
Synchronize with doing shared lock control for reference,
The flag notification unit 142 is instructed to refer to the buffer discard table 150. The flag notification unit 142 searches the buffer discard table 150 for a list corresponding to page P1 (step S502). If the corresponding list is not detected, the notification corresponding to the acquisition of the shared lock and the second flag (OFF) is transmitted to the host computer 100-2 as the reference request source (step S521).

If the corresponding list is detected in step S502, the "resource" page P of the list is detected.
1 and the "device" referring to the cell corresponding to the host computer 100-2, the first and second flags (ON, OF
It is referred to which state of F) (step S).
503). Here, if the first flag state (ON), the request for the signal notifying the acquisition of the shared lock and the signal "buffer discarding required" indicating that the target data resource needs to be discarded from the buffer is requested. It is transmitted to the original host computer 100-2 (step S504). Figure 6
The buffer discard table 150 of FIG.
This is a state in which a reference request has been made from the host computer 100-2 subsequent to the above state, and the list of page P1 of “resource” has already been registered. In this FIG.
The corresponding cell has the first flag "ON", indicating that "buffer discard is required". Buffer 106-
2 indicates that the page including the data A and Z is discarded and the page including the data B and Z is newly read. If the second flag state (OFF), the request source sends a signal notifying the acquisition of the shared lock and a "buffer discarding rejection" indicating that it is not necessary to discard the target data resource from the buffer. To the host computer 100-2 (step S511).

The host computer 100 which has received the "buffer discarding required" notification signal in step S504-
In step 2, the buffer discard processing unit 110-2 discards the page P1 that is the corresponding resource in the buffer 106-2 (step S505). The host computer 100-2, which has received the “buffer discarding rejection” notification signal in step S511, can refer to the data by using the page P1 already stored in the buffer 106-2. If the corresponding list in step S521 does not exist, the host computer 100-2 is in a state in which the data resource has not been read into the buffer 106-2, or is in a state where only the reference process is performed. , In this case, the discarding process of the buffer is not performed.

The host computer 10 by the user
Record R of shared database 174 via 0-2
1 is referred to, and the reference process ends (step S5).
06, S512, S522).

Steps S506, S512 and S52
With the completion of the reference processing of No. 2, the exclusive control device 130 is notified of the shared lock release request. Step S506
In this case, the flag setting unit 144 changes the corresponding cell in the corresponding list in the buffer discard table 150 to the second flag (OFF) (step S).
507). In step S507, as shown in FIG. 7, in the buffer discard table 150, the reference processing is performed on the host computer 100-2 and the page P.
The cell corresponding to 1 is changed from the first flag (ON) to the second flag (OFF). Step S512
In this case, the list flag changing process is not particularly performed. In step S222, since the list does not originally exist, the reference process is ended as it is.

Next, after the processing of steps S507 and S512, the list deletion unit 146 searches whether or not all the cells of the corresponding list have the second flag (OFF) (step S531). All cells have the second flag (O
If it is FF), this list is deleted (step S532). In this step S532, for example, as shown in FIG.
, All the lists corresponding to page P1 are second
If the flag is OFF (OFF), this list will be deleted from the buffer discard table 150. As a result, it is possible to suppress the swelling of data in the buffer discard table 150.

After that, the shared lock in the data resource requested to be referred to is released, and a notification of the release is sent to the requesting computer 100-2 (step S533).

As described above, the data of each page resource unit stored in the buffer of each host computer is matched with the reference processing in synchronization with the reference control, so that the data is read from the database. Efficient use of data in the buffer of the host computer, reduction of communication with the database storage device for reading data, and page resource accumulated in the buffer can be discarded appropriately. The system can be realized.

(Modification of Database Sharing System) The present invention is not limited to the examples described with reference to FIGS. 1 to 8 described above, and various modifications can be made without departing from the scope of the invention. Is. For example, the list addition process in step S223 in FIG. 2 does not necessarily have to be performed after step S222, and may be performed after the corresponding list is not detected in step S202, for example.

In the above embodiment, the processing program for discarding the buffer that performs the processing of each processing unit in the host computer and the exclusive control device that operates the database sharing system, and the processing in the above-described modification is applied to the application. The software may be stored in a recording medium such as a hard disk. This makes it possible to store the program or the like in a portable recording medium such as a CD-ROM and sell or carry it.

[0049]

By using the database sharing system according to the present invention, the matching of the data in page units stored in the buffer of each host computer is synchronized with the update / reference processing during the update / reference control. By doing so, it is possible to efficiently use the data in the buffer of the host computer read from the database and to reduce the communication with the database storage device for reading the data. The accumulated page resources can be discarded appropriately.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining an example of the overall configuration of a database sharing system according to the present invention.

FIG. 2 is a flowchart for explaining an operation at the time of a data update process of the database sharing system of FIG.

FIG. 3 is a block diagram illustrating a part of the operation of the branch process together with the flowchart of FIG. 2 (No. 1).

FIG. 4 is a block diagram illustrating a part of the operation of the branch processing together with the flowchart of FIG. 2 (No. 2).

5 is a flowchart for explaining an operation at the time of data reference processing of the database sharing system in FIG.

FIG. 6 is a block diagram illustrating a part of the operation of the branching process together with the flowchart of FIG. 5 (No. 1).

FIG. 7 is a block diagram illustrating a part of the operation of the branch process together with the flowchart of FIG. 5 (No. 2).

FIG. 8 is a block diagram illustrating a part of the operation of the branch process together with the flowchart of FIG. 5 (No. 3).

[Explanation of symbols]

10: Database sharing system 12, 14: Communication line 100: Host computer 102, 132, 172: communication interface 104: main memory 106: buffer 110: Buffer discard processing unit 130: Exclusive control device 134: Exclusive control unit 140: Buffer discard table processing unit 142: Flag notification unit 144: Flag setting unit 146: List deletion unit 150: Buffer discard table 170: Database storage device 174: Shared database

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shuji Shimada             6-81 Onoe-cho, Naka-ku, Yokohama-shi, Kanagawa             Hitachi Software Engineering Stock Association             In-house F-term (reference) 5B082 FA17

Claims (5)

[Claims] 1. A database storage device that stores data resources shared by a plurality of information processing devices having a buffer, and access exclusive control for access requests to the desired data resources from the information processing devices. In the database sharing system having an exclusive control device for performing the exclusive control device, the exclusive control device stores data stored in the buffer in a list corresponding to each of the information processing devices and each of the data resources in the database storage device. First to represent the disposal of resources
Flag indicating that the data resource is not discarded
And a buffer discard table storing the flag of the information processing device, based on an update request from the information processing device to the data resource of the database storage device, if the corresponding list is detected, among the buffer discard table,
With reference to the cell corresponding to the information processing device and the data resource, a notification is made as to whether any of the first and second flags is recorded, and if the corresponding list is not detected, And a flag notification unit that sends a notification corresponding to the second flag to the information processing apparatus, and when the information processing apparatus receives the notification related to the first flag, the data resource is stored. In this case, the exclusive control device further includes a buffer discarding unit for discarding the information, and the exclusive control device further includes the information in the buffer discard table based on the update processing of the data resource of the database storage device by the information processing device. The second flag is recorded in the cell corresponding to the processing device and the data resource, and the cell is stored in the cell corresponding to the data resource other than the information processing device. A database sharing system comprising a flag setting means for recording a first flag. 2. A database storage device that stores data resources shared by a plurality of information processing devices having a buffer, and access exclusive control for access requests to the desired data resources from the information processing devices. In the database sharing system having an exclusive control device for performing the exclusive control device, the exclusive control device stores data stored in the buffer in a list corresponding to each of the information processing devices and each of the data resources in the database storage device. First to represent the disposal of resources
Flag indicating that the data resource is not discarded
A buffer discard table storing a flag of the information processing device, and based on a reference request from the information processing device to a predetermined data resource of the database storage device, if the corresponding list is detected, among the buffer discard table, By referring to the cell corresponding to the information processing device and the data resource, a notification is made as to which of the first and second flags is recorded, and if the corresponding list is not detected, the second Flag notification means for making a notification corresponding to the flag to the information processing apparatus, and the information processing apparatus, when receiving the notification related to the first flag, if the data resource is stored. And a buffer discard means for discarding it, wherein the exclusive control device further refers to the information processing device for referring to the data resource of the database storage device. On the basis of the above, if a corresponding list is detected from the buffer discard table, a flag setting means for recording the second flag in the cell corresponding to the information processing device and the data resource in the list is provided. A database sharing system characterized in that 3. The database sharing system according to claim 2, wherein the exclusive control device further has, after the recording by the flag setting means, all cells of the list have a second flag, A database sharing system comprising list deleting means for deleting the list. 4. A database storage device that stores data resources shared by a plurality of information processing devices having a buffer, and access exclusive control for access requests to the desired data resources from the information processing devices. A buffer discarding method in a database sharing system having an exclusive control device for performing the exclusive control device, wherein the exclusive control device includes a list corresponding to each of the information processing devices and each of the data resources in the database storage device. A first representing discarding the data resource stored in the buffer
Flag indicating that the data resource is not discarded
And discarding the predetermined data resource of the buffer of the information processing apparatus based on the buffer discard table storing the flag of the information processing apparatus, and updating the data resource of the database storage apparatus by the information processing apparatus. If there is, the second flag is recorded in the cell corresponding to the information processing device and the data resource in the buffer discard table, and the data resources other than the information processing device and the data resource are recorded. If the first flag is recorded in the cell corresponding to and the reference processing for the data resource of the database storage device is performed by the information processing device, the corresponding list is deleted from the buffer discard table. Is detected, the second flag is recorded in the cell corresponding to the information processing device and the data resource in the list, and A buffer discarding method in a database sharing system, wherein after the recording, if all cells of the list have a second flag, the list is deleted. 5. A buffer discard processing program in a database sharing system for causing a computer to execute each processing of the buffer discarding method in the database sharing system according to claim 4.