JP3475783B2 - Method for controlling sharing of database definition information between processes - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a database control system, and more particularly to a system for sharing database definition information among multiple processes.

[0002]

2. Description of the Related Art Conventionally, a database control system using a shared memory of this type has been used for the purpose of reducing memory by sharing and improving performance. As a database control system that enables sharing of procedures for database operations among multiple process pipes, improves memory usage efficiency, and reduces the time required for developing database procedures, for example, Japanese Patent Laid-Open No. 9-319643 discloses: When multiple processes simultaneously request the same database operation procedure to be expanded, a means for controlling the expansion request, a means for sharing the database operation procedure among multiple processes, and a database in a shared memory space between multiple processes A system provided with means for managing an area in which operation procedures are developed is proposed. In this system,
Information sharing is realized by controlling the count of the information expanded on the memory (having the ID of the object and the usage count of the process using the object in the sharing control table).

[0003]

However, the above-mentioned conventional database control system has the following problems.

The first problem is that if the definition information is changed while the information is being shared and used, the shared information will be incorrect, but in the conventional system. That is, I cannot sense this.

The reason for this is that it does not take into account the situation in which the information becomes invalid by executing a ROLLBACK instruction that aborts the current transaction and cancels all updates made by this transaction.

The second problem is that when the information is shared and used, the information cannot be invalidated at an arbitrary timing.

The reason is that the shared information is only managed, and individual information of each process sharing the information is not held.

A third problem is that if there is no shared process, the information expanded in the memory becomes invalid, and the next time the same information is referenced, it will not become valid, so that performance improvement cannot be expected. That is.

The reason for this is that, in preparation for a change in definition, if there is no process, the information is invalid and is not reused.

Therefore, the present invention has been made in view of the above problems, and an object thereof is to share information to improve performance, and further improve reliability and operability, and increase speed. The purpose is to provide a system.

[0011]

In order to achieve the above object, the present invention provides a shared memory search means for searching target information from a shared memory, a shared memory registration means for registering information in the shared memory, and process information. And process information registration means for registering.

In the present invention, the shared memory preferably has the resource name, the definition information, the definition process information and the process information for accessing the resource, and the status information indicating whether the resource is in use. And flag information indicating whether or not the definition has been deleted. Definition SQL
(Structured Query Language) This information is retrieved and used by the shared memory retrieval means at the time of statement execution. Further, at the time of executing the SQL statement of the definition system, it is possible to determine whether the already expanded shared information is valid or invalid by changing the state.

According to the present invention, even when the definition information is changed, the shared memory is preferentially used so that the shared memory can operate without degrading the performance, and even if another process uses the same information, When it is desired to change, it is possible to control immediately, and when referring to the same definition information, the shared memory is referred to, which speeds up.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a system configuration of an embodiment of the present invention. Referring to FIG. 1, according to the embodiment of the present invention, a shared memory space 2 in which specific information can be shared between processes is provided for a user memory space 1 in which the programs are expanded when the programs A and B are executed. The system to be held has a shared memory operating means 3 for operating a shared memory, a definition information database 4 in which definition information is registered in advance, and a database group 5 which holds actual database data.

The shared information 21 in the shared memory space 2 includes a state (used and unused) 211, a flag 212, and a resource name 21.
3, the definition information 214, the definition process number 215, and the process number (process ID) 216 are included as one entry, and are managed by the management number (1 to nnnnn).

The shared memory operating means 3 comprises a shared memory searching means 31, a shared memory registering means 32, and a process information registering means 33.

The shared memory retrieving means 31 obtains its definition information from the shared memory space 2 using the given resource name as a key.

The shared memory registration means 32 expands the definition information in the shared memory space 2 from the definition database 4 using the resource name as a key.

The process information registration means 33 registers the process information allocated to the user memory space 1 when each user program is executed in the shared memory space 2 using the resource name being used as a key, and COMMIT ( (Commit) / ROLLBACK (rollback) command, and the definition information expanded in the shared memory space 2 is updated in accordance with the addition, deletion, or change of the resource definition information.

The functions of the shared memory search means 31, shared memory registration means 32, and process information registration means 33 are realized by programs executed on a computer that manages a database.

FIG. 2 is a flow chart for explaining the processing flow of the embodiment of the present invention. The operation of this embodiment will be described in detail with reference to FIGS. 1 and 2.

The user program 1 executes an SQL (structural query language) command for a certain resource (step A1), and the shared memory search means 31 is activated (step A2).

The shared memory search means 31 searches the resource name 213 of the shared information 21 in the shared memory space 2 using the resource name used by the user program 1 as a key.

As a result of the search, if the corresponding resource name is not found (step A3), the shared memory registration means 32 is activated (step A5).

The shared memory registration means 32 accesses the definition information database 4, newly adds the definition information of the designated resource to the shared information 21 in the shared memory space 2, and activates the process information registration means 33. (Step A6).

On the other hand, in step A3, if the resource name is found as a result of the search by the shared memory searching means 31, the deletion flag 212 of the same entry as the corresponding resource name in the shared information 21 is confirmed (step A4).

At step A4, the deletion flag 212
Is off, the state 211 in the shared information 21 is checked, and if it is in the "unused" state, it is set to "in use" and the process information registration means 33 is activated (step A6). If "in use", The process information registration means 33 is activated as it is.

On the other hand, in step A4, if the deletion flag 212 is on, the resource is already released by another process, so the state 211 is checked. State 21
If 1 is "in use", the definition is deleted by another process, and since the quiesce point is not established, it is determined that the quiesce cannot be executed, and the SQL instruction is abnormally terminated as error processing (step A9). ).

If it is not used, the definition deletion in another process is completed, so it is judged that the definition may have been changed, and the shared memory registration means 32 is activated.

The process information registration means 33 registers the process number of the corresponding process in the process number 216 of the shared information 21.

The user program 1 defines the definition information 214 registered in the shared information 21 (attributes and lengths of constituent columns,
Database group 5 with reference to whereabouts of database)
To access. At the end of the user program 1, the process information registration means 33 is activated and the process number 21
The process number of the corresponding process registered in 6 is deleted, and if all process information is not entered, the state 211 is returned to unused.

By these processes, once the definition information is retrieved from the definition information database 4, the definition information database 4 is not accessed until the definition information is deleted, and the shared information in the shared memory space 2 is not accessed. With reference to, the database group 5 can be accessed.

FIG. 3 is a flow chart for explaining the processing flow of the embodiment of the present invention, and shows the processing flow when the definition addition type SQL instruction is executed. The operation when the definition addition type SQL instruction is executed will be described with reference to FIG.

When an SQL command that defines a resource is executed from the user program 1 (step B1), the shared memory search means 31 is activated (step B2), and the resource name which is the key of the information defined from the shared information 21. Is resource name 2
If it is not registered as a result of the search (step B4), the shared memory registration means 32 is activated (step B7).

The shared memory registration means 32 accesses the definition information database 4 and checks whether or not the definition information and this definition addition do not conflict (step B8). If they do not conflict, the process information registration means 33 is activated. (Step B9).

On the other hand, if there is a contradiction in step B8, it is judged that this definition addition instruction is abnormal, and error processing is performed (step B11).

On the other hand, if it is found as a result of the search by the shared memory search means 31, the state 211 of the shared information 21 is confirmed, and if it is in the "in use" state ("in use" branch in step B4). ), The definition process number of the shared information 21 is compared with the own process number (step B5), and if it is the own process number, it is verified whether or not the definition information 214 and the addition of the definition information performed this time are consistent (step B5). B8).

In step B5, if it is not the own process, the operation in other processes will be hindered, so the execution of the definition addition SQL command is terminated and error processing is performed (step B11).

In step B4, the state 211 is "unused", and in step B6 the deletion flag 21
If 2 is not set (NO branch of step B6), the definition information is verified at step B8. If there is no contradiction, in step B9 the process information registration means 3
Start 3.

On the other hand, if the state 211 is unused and the deletion flag 212 is set in step B4,
It is considered that the definition has been changed by another process, and the shared memory registration means 32 is activated (step B7).

The process information registration means 33 registers the process information in the corresponding column of the shared information 21, and
Since it is defined in this process, the process number of the corresponding process is also registered in the defined process number 215.

Finally, when the program ends, the process number of the corresponding process registered in the shared information 21 is deleted,
If all process information is not entered, the status is returned to "unused".

FIG. 4 is a flow chart for explaining the processing flow of the embodiment of the present invention, and shows the processing flow when the definition deletion type SQL instruction is executed. The operation when the definition deletion type SQL instruction is executed will be described with reference to FIG.

When an SQL instruction for deleting a resource from the user program 1 is executed (step C1), the shared memory searching means 31 is activated (step C2), and the resource name as a key of the information to be deleted from the shared information 21 is displayed. Is registered, and the result of the search (step C3). If it is not registered, the definition information database 4 is directly accessed and the result is returned, and the command is terminated.

In step C3, if the resource name which is the key of the information to be deleted is found as a result of the search, the status 212
If it is "in use"("unused" branch in step C4), the process information 216 is referred to. If the process information 216 is only the process number of its own process (YES branch in step C6), share The memory registration means 32 is activated (step C6). The shared memory registration means 32 accesses the definition information database 4, deletes the definition information, and activates the process information registration means 33 (step C7).

In step C5, if other process information is registered, the process cannot be performed, so it is determined that the result is abnormal and the process proceeds to error processing (step C9).

If the state 212 is "unused" in step C4, the shared memory registration means 21 is activated (step C6). The process information registration means 33 registers the information of the process and turns on the deletion flag 211 of the shared information 21 because it is a deletion type.

Next, at the end of the program, the shared information 2
The process number of the corresponding process registered in 1 is deleted, and if all process information is not entered, the status is returned to "unused".

FIG. 5 shows C in the embodiment of the present invention.
9 is a flowchart for explaining a processing flow when an OMMIT / ROLLBACK instruction is executed. Referring to FIG. 5, COMMIT / RO in the embodiment of the present invention
The operation when the LLBACK instruction is executed will be described.

Referring to FIG. 5, if the COMMIT instruction is executed (step D3), which normally terminates the current transaction and makes all updates made by this transaction visible to other transactions, the shared memory. The search means 31 is activated (step D4). The shared memory search means 31 refers to the defined process number 215 of the shared information 21 by using the process number of the corresponding process as a key, and confirms whether or not the same process number is registered. If the number of the same process is registered (YES in step D5), the process information registration means 33 is activated (step D6). The process information registration means 33 deletes the definition number of the relevant process registered in the definition process number 215.

When the ROLLBACK instruction is executed (step D3), the shared memory searching means 31 is activated (step D4). The shared memory search means 31 uses the process number of the corresponding process as a key to share information 2
By referring to the defined process number 215 of No. 1, it is confirmed whether or not the same process number is registered (step D).
5). If the same process number is registered, the process information registration means 33 is activated (step D6). The process information registration means 33 deletes the process number of the corresponding process registered in the defined process number 215, and turns off if the deletion flag 211 is on and turns on if the deletion flag 211 is off.

As a result, when the process whose definition has been changed is rolled back (rolled back), it is possible to avoid erroneous operation by illegally referring to the registered shared memory information.

[0054]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 6 is a diagram for explaining one embodiment of the present invention.

Referring to FIG. 6, in one embodiment of the present invention, the programs E1, E3, E4 are respectively labeled with AB.
It includes an SQL statement that defines the C table, an SQL statement that processes the database using the defined ABC table, and a COMMIT / ROLLBACK command that establishes a quiesce point.

The shared information 2 includes the definition information of the ABC table and is connected to the definition information database 5.

Next, an embodiment of the present invention will be described. First, when the program E1 is started and an attempt is made to define the table ABC, the shared memory search means 31 is started, and since the ABC information is not registered in the shared information E2, the shared memory registration means 31 is started and the definition information database 5, the related definition information is read, the definition information of the ABC table is registered, and the definition content of the table ABC is expanded in the shared information 2.

Next, the process information definition means 33
The process number of the corresponding process is registered in the definition process and process information of the shared information 2.

Next, a request to delete the ABC table is made from the program E3. However, since the registered defined process number and the process number are different, the execution result becomes abnormal.

Next, when the process of accessing the database from the program E3 using the ABC table operates, the process information registration means 33 registers the process information.

Although an attempt was made to delete the ABC table from the program 1, the process result of the shared information 2 has a process number other than its own process (here, the program E3) registered, so the execution result becomes abnormal. After the program E3 ends, the program E4 is started and tries to define the ABC table. However, since the shared memory search means 31 finds information and the definition process is not its own process, the execution result becomes abnormal.

In the program E1, when the ABC table is requested to be deleted after the COMMIT instruction is executed, the program E3
Since the process has been completed, the shared memory registration means 31 is started and the information in the ABC table is deleted from the definition information database 5 because the only process in use is the own process. afterwards,
When the ABC table is used, the deletion flag of the shared information 2 has already been turned on, so it is determined that the deletion has been completed, and the execution result becomes abnormal.

When the ROLLBACK instruction is executed next, the deletion flag is turned off, and the program E4 sends an AB
It becomes possible to use table C.

[Second Embodiment] Next, a second embodiment of the present invention will be described in detail with reference to the drawings. Figure 7
[Fig. 8] is a diagram for explaining a processing flow of the second embodiment of the present invention.

Referring to FIG. 7, in the second embodiment of the present invention, the process invalidating means (step F) is added to the process of executing the definition deletion instruction shown in the flowchart of FIG.
6) is added.

This process invalidating means (step F6)
Is activated when a plurality of processes are using the corresponding table as a result of searching by the shared memory searching means 31. The process invalidating means sends a notification to a process other than its own process in order to forcibly disconnect the resource.

Here, it is assumed that the running program G1 receives the notification. If the program G1 has established the quiesce point at the stage of receiving the notification, the close processing is performed on the notified resource (step G5). On the other hand, if the stationary point is not established in step G3, COMM
The closing process is delayed until the IT command or the ROLLBACK command is executed (step G4).

When the closing process of all the processes notified of the process invalidation is completed, the process information 2 of the shared information 21
In 16 there are no process numbers for other processes.

When all the processes other than the own process are lost, the shared memory registration means 32 is activated.

In the second embodiment of the present invention, by forcibly releasing the resource from the process using the resource to be deleted, the definition can be deleted at an arbitrary timing even when it is being used by another process. Can be done.

[0071]

As described above, the present invention has the following effects.

The first effect of the present invention is that by sharing the definition information expanded in the shared memory, the performance of programs that use the same resource can be improved.

The reason is that in the present invention, the definition information is not immediately deleted from the shared memory even if there are no processes to refer to, so that the definition information can be reused when the same table is referred to for the second time and thereafter. This is because it is not necessary to access the definition information database.

The second effect of the present invention is that even if the definition information of the table is changed, it can be sensed, and while maintaining the effectiveness of shared memory utilization, even when the definition is changed, incorrect information is read and malfunction occurs. It means that there is nothing.

The reason is that in the present invention, COMM is used.
This is because it is possible to identify whether the definition information is valid or invalid when executing the IT and ROLLBACK commands.

The third effect of the present invention is that the resource information can be deleted at an arbitrary timing even when a certain resource is shared and used.

The reason is that in the present invention, it is possible to notify each process that the resource cannot be used by managing the process information in the shared memory.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a flow chart showing a processing flow of the first embodiment of the present invention.

FIG. 3 is a flowchart showing a processing flow of the first embodiment of the present invention.

FIG. 4 is a flowchart showing a processing flow of the first embodiment of the present invention.

FIG. 5 is a flow chart showing a processing flow of the first embodiment of the present invention.

FIG. 6 is an explanatory diagram for specifically explaining the first embodiment of the present invention.

FIG. 7 is a flowchart showing a processing flow of the second embodiment of the present invention.

[Explanation of symbols]

1 program 2 shared memory space 3 shared memory operation means 4 definition information database 5 database group 21 shared information 31 shared memory search means 32 shared memory registration means 33 process information registration means 211 state 212 delete flag 213 resource name 214 definition information 215 corresponding table Process number 216 that defines the process number that uses the corresponding table (repeated)

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference Atsushi Iizawa, Data definition management of database management system G-BASE, Information Processing Society of Japan 35th Meeting (Late 1987) National Conference, Japan, Information Processing Society of Japan , September 28, 1987, Volume (I), p. 399, 400 Hideki Sunahara, USENIX '90 Summer Report, UNIX MAGA ZINE, Japan, ASCII Corporation, September 1, 1990, Vol. 5, No. 9 (Vol. 47), p. 28 −− 32 (58) Fields investigated (Int.Cl. ⁷ , DB name) G06F 12/00

Claims (5)

(57) [Claims] 1. A database control system for storing definition information required for accessing a database from a plurality of user processes in a shared memory and sharing the definition information among a plurality of user processes, wherein the shared memory is shared information. Resource names of tables and the like in the database, and the attributes and lengths of columns related to the resources,
Definition information such as whereabouts of the database, information of the definition process and the process of accessing the resource, and status information indicating whether the resource is being used, deletion flag information indicating whether the definition has been deleted, include, if the instructions defining the resources in the user process has been executed, the shared memory, and search resource name as a key, and the shared memory retrieval means for acquiring definition information relating to the resource, the shared memory retrieval means If the resource name is not found as a result of the search in, the shared memory registration means for reading the definition information from the definition information database in which the definition information has been registered in advance using the resource name as a key, and expanding and registering in the shared memory, process information for the user process, and a process information registration means for registering in the shared memory the resource name as a key, the user An instruction for a resource that is a process is executed and
The shared memory search means searches using the resource name as a key ("
As a result of "Search 1"), the resource name is found.
If the deletion flag corresponding to the resource name is set,
Check whether or not it corresponds to the resource name if set
Check the status information, and if it is not used,
Activate the memory registration means, and if it is in use, handle it as an error.
Control is performed to terminate the above instruction abnormally, and if the user process executes the instruction of definition addition type,
Search by the shared memory search means (referred to as "second search")
As a result, if the resource name is found,
Check the corresponding status information, if the status information is not
If used, the deletion flag corresponding to the resource name
If is not set, the definition information is verified and verified.
If there is no contradiction, the process information registration means
A database control system, characterized in that control is performed to start and register process information . 2. The resource name is not found as a result of the first search.
If a deletion flag is set, the deletion flag corresponding to the resource name is set
Check if there is any, and if the deletion flag is not set,
If the status information corresponding to the resource name is unused,
If so, the process information registration means is started as being in use, and as a result of the first search, the corresponding resource name cannot be found.
If so, the shared memory registration means is activated and the shared memory is registered.
The memory registration means can access the definition information database.
Add the definition information of the specified resource,
2. The database control system according to claim 1 , wherein control for activating the process information registration means is performed . 3. The resource is found as a result of the second search.
Check the status information corresponding to the resource,
If it is in the status, the definition process number of the shared information and its own process
The process number is compared with the process number, and if the process number is
Information and whether the definition information added this time is consistent.
Proof, and if it is not its own process, execute the instruction of definition addition type
Is terminated, error processing is performed, the status information corresponding to the resource is unused, and the deletion flag
If the lag is set, the definition is changed from another process
The shared memory registration means is started.
That, characterized in that, the database control system according to claim 1, wherein. 4. If you want to delete the resources defined in the user process instruction is executed, if the shared memory search means to search the key resource name the shared memory, found search results, the resource use If the resource is being used by its own process and it is being used by another process, the resource is forced to the other process. And a process for deleting the process information by forcibly canceling the process of the other process, deleting the definition information, turning on a deletion flag corresponding to the definition information, and deleting the process information. The database control system according to claim 1, wherein: 5. A database control system for storing definition information required for accessing a database from a plurality of user processes in a shared memory and sharing the definition information between a plurality of user processes, wherein the shared memory uses the database as the shared information. Resource names such as tables in the table, and the attributes and lengths of the columns related to the resources,
Definition information such as the location of the database, information on the definition process and the process for accessing the resource, status information indicating whether the resource is being used, and deletion flag information indicating whether the definition has been deleted. , hints, (a) if the instruction in the user process to define the resource has been executed, the shared memory search process for acquiring definition information for the previous <br/> Symbol resource searching a key resource name the shared memory (B) If the resource name is not found as a result of the search in the shared memory means, the definition information is read from the definition information database in which the definition information is registered in advance by using the resource name as a key, and the shared memory is expanded in the shared memory. registration process, (c) the process information of the user process, the process information registration process for registering in the shared memory the resource name as a key, (d) user Instruction execution is for resources is process
The shared memory search means using the resource name as a key
As a result of (called "first search"), the resource name is found
If the deletion flag corresponding to the resource name is set,
Check whether the resource name is correct, and if it is set, support the resource name
Check the above status information, and if it is not used,
If the memory registration means is activated and is in use, error processing is performed.
As a process for controlling to terminate the above instruction abnormally, (e) A definition addition type instruction is executed in the user process
In this case, the search by the shared memory search means (“second detection
If the resource name is found as a result of
Check the status information corresponding to the resource name, check the status
If the information is unused, the deletion corresponding to the resource name
If the removal flag is not set, the definition information is verified.
If there is no contradiction as a result of verification, the above process information registration
A recording medium recording a program for causing the computer to execute each of the above means (a) to ( e ) of the process of activating the recording means to register the process information .