JPH04130936A - Control system for simultaneous access to file - Google Patents

Abstract

PURPOSE:To improve the through-put of the whole system by storing updated contents by means of an updated journal record without directly updating the block of a data file developed in a buffer of a memory, and at the time of setting up a check point, reflecting the updated contents for the buffer and rewriting the reflected contents in the data file. CONSTITUTION:A user program 1 requests the reference/updating of a record in the data file 8 which is occasionally required in its processing process to a data access program 2. The request from the program 1 is inputted to an exclusive control means 3 in the program 2 and the means 3 decides whether the request is to be received, to be waited because of being used by another program, or to be rejected because of the generation of deadlock with another program in accordance with a known method, and in the case of reception, transfers the input of a reference request to a buffer control means 4 or transfers the input of an updating request to an updated journal control means 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a simultaneous file access control system, and particularly to a record-based exclusive control system.

[Conventional technology]

When a data file is shared by a plurality of processes (programs), it is necessary to perform access control W (exclusive control) to prevent conflicts in data contents.

By the way, access control is often performed in units of blocks, which are input/output units of data files, for ease of management, but according to this, the area occupied by one process is wide, and it is difficult to wait for other processes. It is desirable to perform access control in units of records smaller than blocks, since this affects processing performance.

For this reason, systems have been provided that control access on a record-by-record basis.

[Problems to be Solved by the Invention] As mentioned above, when access control is performed on a record-by-record basis, the range occupied by one process is narrow, which is preferable, but file rollback in the event of deadlock or abnormal termination is In order to make this possible, it is necessary to collect not only post-update journals but also pre-update journals, and this collection of pre-update journals has the drawback of reducing processing performance.

In other words, in general, when referencing and updating a data file, the necessary blocks are read from the data file into a buffer in memory, and then referenced and updated.
With block-based access control, file rollback is possible by enabling updates for the entire block on the buffer, but with record-based access control, update records that are valid within one block must be disabled. This results in a mixture of updated records, and a pre-update journal is required to restore the invalidated records to their original contents.

The present invention has been proposed in view of the above points, and its purpose is to enable efficient record-based access control without collecting pre-update journals,
The object of the present invention is to provide a file simultaneous access control method that can improve the throughput of the entire system.

[Means to solve the problem]

In order to achieve the above object, the present invention provides exclusive control means for managing simultaneous access necessary for referencing and updating records in a data file from multiple processes, and for managing a large-scale memory space and for managing multiple a buffer control means that allocates, releases, and performs physical input/output of buffers in block units of data files for the process; and a buffer control means that generates an updated journal record if there is no corresponding updated journal record in memory when updating; a post-update journal control means that updates the post-update journal record, if any, and manages it in memory along with the identifier of the process for each block until execution of a checkpoint or file roll puncture; The apparatus includes checkpoint means for outputting the updated journal record to the updated journal storage file and reflecting it in the buffer, and then outputting the buffer contents to the data file to set a static point.

[Effect]

In the file simultaneous access control method of the present invention, the exclusive control means manages simultaneous access necessary for referencing and updating records in the data file from multiple processes, and the buffer control means manages the large-scale memory It manages the space, allocates/releases buffers, and performs physical input/output for multiple processes in block units of data files, and when updating, if the post-update journal control means does not have a corresponding post-update journal record in memory, it updates the data file. Generates a post-journal record, updates the post-update journal record if any, and manages each block in memory along with the corresponding process identifier until a checkpoint or file roll hack is executed, and performs a checkpoint according to a checkpoint request. The means outputs the updated journal record of the corresponding process to the updated journal accumulation file and reflects it in the buffer, and then outputs the buffer contents to the data file to set a quiescent point.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the simultaneous file access control method of the present invention.

In FIG. 1, this embodiment has a user program 1,
data access program 2, data file 8,
It is composed of an updated journal accumulation file 9. The data access program 2 also includes exclusive control means 3, buffer control means 4, post-update journal control means 5, checkpoint means 6, and file rollback means 7.

The functions of each part are outlined below.

User program 1: This is a business program that includes references and updates to records in the data file 8.

Data access program 2: Accesses data file 8 in response to a request from user program 1.
This is a very useful program.

Exclusive control means 3: This is a part that manages simultaneous access necessary for referencing and updating records in the data file 8 from a plurality of processes (user programs 1).

Buffer control means 4: This is a part that manages a large-scale memory space (not shown) and performs buffer allocation, release, and physical input/output for each block of the data file 8 for a plurality of processes. The details of the process are as shown in FIG.

Post-update journal control means 5: When updating, if there is no corresponding post-update journal record on the memory, a post-update journal record is generated, and if there is, it updates the post-update journal record, and performs a checkpoint or file rollback. This is the part that manages updated journal records in memory along with the identifier of the corresponding process for each block until execution. The details of the process are as shown in FIG.

Checkpoint means 6: In accordance with the checkpoint request from the user program 1, outputs the updated journal record of the corresponding process to the updated journal accumulation file 9, reflects it in the buffer, outputs the buffer contents to the data file 8, and stops it. This is the part where you set the points.

The details of the process are shown in FIG.

File roll hacking means 7: This is a part that discards the updated journal record of the corresponding process held in the memory when a program abort or deadlock occurs, and guarantees the file contents at the immediately previous quiescent point. The details of the process are as shown in FIG.

Data file 8: This is a file to be referenced and updated.

Post-update journal accumulation file 9: This is a file that accumulates post-update journal records.

The operation of the above embodiment will be described below with reference to FIGS. 1 to 5.

In FIG. 1, a user program 1 requests a data access program 2 to refer to and update records in a data file 8 as necessary during the processing process. In addition, when making an update request, the record pointer and the updated record image are sent to the data access program 2.
pass it on to

The request from the user program 1 is taken into the exclusive control means 3 of the data access program 2, and the exclusive control means 3
uses a well-known method to determine whether to accept this request, make it wait because it is being used by another program, or reject it because a deadlock will occur with another program. , when accepting, if it is a reference request, that fact is passed to the buffer control means 4, and if it is an update request, that fact is passed to the post-update journal control means 5.

If the resource is being used by another program, user program 1 is suspended until the resource is released, and the request is accepted when the resource is released. If it is an update request, it is passed to the post-update journal control means 5.

If a deadlock state is established with another program, the user program 1 is notified of this fact.

The processing of the buffer control means 4 when the reference request from the user program 1 is accepted will be explained below with reference to FIG.

Buffer control means 4 that received the notification (resource reservation notification)
checks whether a block containing the requested record of data file 8 already exists in the memory sofa (step 41), and if it does exist (YES in step 41).
S) has user program 1 associated with this block.
Step 42: Search the updated journal records related to the update and find one that corresponds to the requested record.
) is present (step 43).

If a corresponding post-update journal record is found (
If YES in step 43), the pointer to the updated journal record is stored and the process returns to user program 1 in step 44).

If the corresponding updated journal record is not found (No in step 43), a pointer to the corresponding record in the block is stored (step 45), and the process returns to the user program 1.

Furthermore, if the block containing the requested record of data file 8 does not exist in the memory (No in step 41), a new buffer area is secured and the corresponding block in the data file is Read (step 46), store the pointer to the requested record in the block (step 45), and return to user program 1.

Next, the processing of the post-update journal control means 5 when the update request from the user program 1 is accepted will be explained below with reference to FIG.

The post-update journal control means 5 that has received the update request,
It is determined whether the requested record is registered as an updated journal record (step 51).

If it is not registered as an updated journal record (YES in step 51), a new area is secured in the memory (step 52), an updated journal record is generated and registered (step 53), and the user program is return.

If it is registered in the memory as a post-update journal record (No in step 51), the content of the post-update journal record is replaced with the post-update record image received along with the update request from the user program 1 ( Step 54) Return to user program.

Next, checkpoint processing will be explained with reference to FIG.

When a series of processing ends, the user program 1 issues a checkpoint means for establishing a stopping point and releasing resources for other programs.

This request is accepted by the checkpoint means 6 of the data access program 2, which causes the data file 8 to reflect the updates made by the user program 1.

That is, as shown in FIG. 4, the checkpoint means 6 extracts the first block of the buffer area (step 61) and determines the existence of the block (step 62).
.

If it does not exist (No in step 62), a resource release request is issued to the exclusive control means 3 (step 69), and the checkpoint process is completed.

On the other hand, if the block exists (YES in step 62)
), it is checked whether there is an updated journal record registered by the user program l (step 63).

If it exists (YES in step 63), the contents of the record corresponding to the updated journal record of the block on the buffer are replaced by the contents of the updated journal record (step 64), and the updated journal record is replaced with the updated journal record. Step 6: Export to journal storage file 9
5), write the block to the data file 8 (step 66), delete the journal record after update (
Step 67).

Then, step 68) takes out the next block from the buffer area, and the process returns to step 62.

On the other hand, if the updated journal record registered by the user program 1 does not exist (step 63
(NO), steps 64 to 67 are not performed.

Next, file roll hack processing will be explained with reference to FIG.

When the user program 1 receives a request rejection notification from the exclusive control means 3 or terminates abnormally, it issues a file roll hack request for the purpose of invalidating data updates made after the previous quiescent point. do.

This request is accepted by the file roll hack means 7 of the data access program 2, and the file roll bank means 7 cancels the updates made by the user program 1.

That is, as shown in FIG. 5, the file rollback means 7 extracts the first program in the buffer area (step 71) and determines the existence of a block (step 7).
2).

If the block does not exist (NO in step 72), a resource release request is issued to the exclusive control means 3 (step 76), and the file roll hack processing is completed.

On the other hand, if the block exists (YES in step 72)
), it is checked whether there is an updated journal record registered by the user program 1 (step 73).

If it exists (YES in step 73), the updated journal record is deleted (step 74). Further, if the updated journal record does not exist (NO in step 73), step 74 is not performed.

Then, step 75) takes out the next block from the buffer area, and the process returns to step 72.

〔Effect of the invention〕

As explained above, in the file simultaneous access control method of the present invention, when multiple processes operate while sharing a data file on a record basis, blocks of the data file developed in a buffer in memory are Rather than updating directly, the updated content is retained using a journal record after the update, and when a checkpoint is set, it is reflected in the buffer and written back to the data file. , it is only necessary to delete the journal records after the update, and there is no need to collect the journal before the update in case of a file roll hack, which has the effect of improving the throughput of the entire system.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the file simultaneous access control method of the present invention, FIG. 2 is a flowchart showing the processing of the buffer control means in FIG. 1, and FIG. 3 is the post-update journal control in FIG. 1. FIG. 4 is a flowchart showing the processing of the checkpoint means in FIG. 1; FIG. 5 is a flowchart showing the processing of the file roll hacking means in FIG. 1. In the figure, l...User program 2...Data access program 3...
・Exclusive control means 4... Buffer control means 5... Post-update journal control means 6...
・Checkpoint method 7...File roll hack method 8...
·data file

Claims (2)

[Claims] (1) An exclusive control means that manages the simultaneous access necessary for multiple processes to refer to and update records in a data file, and a large memory space that manages the data file for multiple processes. A buffer control means that allocates, releases, and physically inputs/outputs buffers in block units, and generates an updated journal record if there is no corresponding updated journal record in memory when updating; A post-update journal control means that updates the post-update journal record for each block and manages it in memory along with the ID of the process until a checkpoint or file rollback is executed; A simultaneous file access control method comprising checkpoint means for outputting to a storage file and reflecting in a buffer, and then outputting the buffer contents to a data file to set a static point. (2) A claim characterized by having a file rollback means that discards the updated journal record of the relevant process held in memory when a program abort or deadlock occurs to guarantee the file contents at the previous quiescent point. File simultaneous access control method described in Section 1.