JPS63280354A - Buffer management system - Google Patents

Abstract

PURPOSE:To reduce the number of times of disk input/output by providing management parts which manage a normal buffer in a normal address space and an extended buffer in an extended address space and taking out data from the extended buffer in case of absence of objective data in the normal buffer. CONSTITUTION:Normal and extended buffers 5 and 8 are provided in normal and extended address spaces 1 and 2 respectively, and normal and extended buffer management parts 4 and 6 are provided in the space 1. A normal buffer management table 9 is used by the management part 4 to check whether a requested page exists in the buffer 5 or not; and if it does not exist there, an extended buffer management table 7 is used by the management part 6 to take out data from the buffer 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a buffer management method suitable for increasing the speed of a database management system.

[Conventional technology]

The conventional buffer management method is disclosed in Japanese Patent Publication No. 57-16
As described in No. 9983, this method manages one buffer. The operation of the buffer management unit in this case is that when a data request occurs, it searches the buffer, and if the requested data exists, it returns the address of the data in the buffer to the request source, and if the requested data does not exist, it searches the buffer and returns it to the external storage device. Retrieve data from a disk file.

[Problem that the invention seeks to solve]

The above conventional technology does not have a means to use a different address space, such as an extended address space, as a buffer. The normal address space is small, and buffered and database management systems use the same normal address space nrJ.
Because the buffer area is placed in Redesigning the buffer management so that it can manipulate extended address space is a method in which the conventional buffer management section passes the address of the data in the buffer to the data request source, so not only the buffer management section but also the data request source can handle the address width. There are problems that require expansion and many program changes. Therefore, in a system such as a database management system that handles large amounts of data or in which a large number of users use a common buffer, the buffer overflows, which inevitably results in frequent disk input/output.

An object of the present invention is to reduce the number of disk input/outputs caused by buffer overflow by making slight changes to conventional programs.

[Means for solving problems]

The above purpose is to have a normal buffer management section that operates and manages the normal buffer provided in the normal address space and an extended buffer management section that operates and manages the extended buffer provided in the extended address space. If the desired data does not exist, this can be achieved by fetching the data from the extended buffer.

[Effect]

When target data does not exist in the normal buffer, the normal buffer management section requests data from the extended buffer management section. The extended buffer management section searches whether data exists in the extended buffer, and if so, transfers the data to the normal buffer specified by the normal buffer management section that is the request source.

The extended address space is wider than the normal address space, and the extended buffer can be secured widely. Therefore, the probability that the target data exists is increased, and the number of disk input/outputs is reduced. Further, changes to the conventional program can be reduced because it is only necessary to call the extended buffer management section.

〔Example〕

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

FIG. 1 shows the overall configuration of the present invention.

1 is a normal address space, and 2 is an extended address space.

3, 4, 5.9 are parts of the database management system, 3 is a page operation section, 4 is a normal buffer management section, and 5 is a normal buffer. A page is a data unit handled by a database management system, and 13.14 corresponds to it. Page operation requests a page to the normal buffer management unit. 19. The operation of normal buffer management will be explained using FIGS. 1 and 2. Step 201 uses the normal buffer management table 9 to check whether the requested page exists in the normal buffer. Step 202 determines whether the page exists as a result of the search, and if so, returns the top address of the page to the request source.Step 214: If not, the process proceeds to step 203. Step 203 determines whether there is an area in the normal buffer to take in the requested page, and if there is, the process moves to 209; if not, the process moves to 204.

Step 204 determines an expulsion page in order to secure an area for import. 2o5 determines whether the evicted page has been updated in the buffer, and if it has been updated, it must be written to disk 9, so 206
Otherwise, the process moves to 208. 2
06 writes the eviction page to disk 21
207 calls the extension buffer management unit 6 and updates the extension buffer 8 (12). This update is performed to prevent data inconsistency between pages in the disk and pages in the expansion buffer 8. The extended buffer update unit 12 will be explained at 208 when the extended buffer management unit is explained later.
16. 200 deletes the evicted page from the normal buffer management table 9. 200 calls the extended buffer management unit 6 to check whether the requested page exists in the extended buffer 8. Reference numeral 10 denotes an extended buffer page search section, which will be explained in detail later when explaining the extended buffer management section. At 210, it is determined whether or not the requested page exists in the expansion buffer. If so, the process moves to 213; otherwise, the process moves to 211.

211 takes out the requested page from the disk and sets it in a free area of the normal buffer. Step 212 calls the extended bath management unit in order to register the page in the extended buffer as well. Reference numeral 11 denotes an extended buffer page registration unit, the detailed operation of which will be explained later. Step 213 registers the newly introduced page in the normal buffer management table. after that,
Returns the first address of the page in the buffer to the request source 1 or more is the normal buffer management section and the description of the normal buffer 0 The normal buffer management section calls the extended buffer management section 6 as described above 20° The details of the operation of the extended buffer management section will be explained next.

As mentioned above, the extended buffer management section includes the extended buffer page search section 10 and the extended buffer page registration section 11.
It has the functions of the extended buffer update section 12. FIG. 3 shows the operation of the extended buffer update section. 30
1 changes the mode to one in which extended address space can be addressed.

Step 302 searches for the page to be updated using the extended buffer management table 7 (18) and determines the location of the page. Step 303 actually updates the page, Step 304 returns the address mode to the original normal address mode, and then the processing returns to the normal buffer management section.

FIG. 4 shows the operation of the extended buffer page search section. 401 is similar to 301.

Step 402 uses the extended buffer management table to check whether the requested page exists in the extended buffer. 40
3 determines whether the page exists as a result of the investigation,
If there is not, the process moves to 405 and reports that there is no corresponding page to the normal buffer management. If there is a requested page, the process moves to 404.

404 transfers the corresponding page into the normal buffer 17;
This page transcription is not part of the normal buffer management unit's operation, but is a feature of the extended buffer management unit.

406 is similar to 304. Thereafter, the process returns to the 1 normal buffer management section.

FIG. 5 shows the operation of the extended buffer page registration section. 501 is similar to 301.

At 502, it is determined whether there is an area in the expansion buffer to store a new page. If there is, the process moves to 505; if there is no area, the process moves to 503. 503 is the same as 204. 5
04 deletes the page determined to be evicted from the extended buffer management table. The difference here from the normal buffer management section is that the page that has been decided to be evicted is always the same value as an in-disk page by the extended buffer update section.
The point is that writing to the disk is unnecessary. 505 transfers the page written to the normal buffer by 211 to the extended buffer. Step 506 registers the newly written page in the extended buffer in the extended buffer management table. 507 is the same as 304, and then the process returns to the normal buffer management section.

The above is a detailed explanation of the extended buffer management section. Through these operations, the page operation 3 can obtain the requested page (15).

In this embodiment, there are few changes to the normal buffer management section, and the extended address space can be used as a buffer. Furthermore, in terms of reliability from the perspective of the database management system, consistency between the disk and the expansion buffer is maintained, and there is no change from the conventional system.

Note that in this embodiment, the number of page inputs from the disk is reduced compared to the conventional method, but the number of page outputs to the disk is not reduced. There are methods such as updating only the extended buffer without outputting to the disk, and outputting to the disk only when the extended buffer overflows and the overflowing page is being updated.

〔Effect of the invention〕

According to the present invention, by using a normal buffer and a larger extended buffer, the probability that the requested data exists in the buffer is increased, and the number of I/Os to the disk file can be significantly reduced, which is effective in speeding up the buffer management method. There is. Furthermore, since the conventional program only needs to be changed to call the expansion buffer management section, the buffer can be expanded easily.

[Brief explanation of drawings]

FIG. 1 is an overall diagram of an embodiment, FIG. 2 is a flowchart of the normal buffer management section, FIG. 3 is a flowchart of the extended buffer update section, and FIG. 4 is a flowchart of the extended buffer page search.
Flowchart FIG. 5 is a flowchart of the extended buffer page registration section. 4... Normal buffer management section, 5... Normal buffer,
6＼〜-2・′:tJ Figure 2 Release 3 Figure Y-14-Figure 5

Claims (1)

[Claims] 1. In a buffer management method of a database management system running on a computer system having a normal address space and an extended address space, a normal buffer that operates and manages a normal buffer provided in the normal address space. a management unit and an expansion buffer management unit that operates and manages an expansion buffer provided in the expansion address space, and extracts the data from the expansion buffer when the target data does not exist in the normal buffer. A buffer management method characterized by: 2. The buffer management method according to claim 1, wherein the extended buffer management unit transfers the data in the extended buffer to the normal buffer.