JPH0248751A - Buffer controlling system for data control system - Google Patents

Abstract

PURPOSE:To effectively use a buffer, and to improve processing efficiency by setting priority order to leave a page in the buffer according to the distinction of the page such as the higher order page, the lower order page and the page of data of an index when the page is read in. CONSTITUTION:A page number to be read in and a buffer request level number of the page from a page requesting person are inputted from an inputting/ outputting means 7. A buffer control table controlling means 4 searches for the requested page from a buffer control table 1, and if the page is not present, it searches for the page of the oldest access history among the pages of the largest level number, and releases the buffer 2 corresponding to it, and rewrites the page number and a page request level, and returns a status and the address of the released buffer 2 to a control part 5. The control part 5 makes the designated page be read in the designated address, and returns the address to the inputting/outputting means 7. Thus, the buffer can be used effectively, and the processing efficiency can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a buffer management method for a database management system operated within a computer system.

〔overview〕

The present invention is a buffer management method for a data management system that reads pages randomly from a file, reserves buffers in memory, and leaves read pages in memory for the number of reserved buffers. By setting the priorities for leaving pages in the buffer depending on whether they are upper pages in the index, lower pages, or data pages, the buffer can be used more effectively and processing efficiency can be improved.

[Conventional technology]

Normally, when randomly reading a randomly organized file, if a page that has been read once is requested to be read again, the physical human output is reduced as much as possible to improve processing efficiency. A buffer for several pages is reserved in memory for this purpose, and if there is a requested page in the buffer, it is configured so that only the address is returned to the page requester without any physical output. .

In this case, when the buffer is fully used,
When there is a read request for a page that is not in the buffer, one of the buffers must be released, and which buffer is released is directly linked to how much physical human output can be reduced, improving performance. This has become a very big problem.

Conventionally, the method for deciding which buffer to release is as follows:
A common LRU control method is to release the buffer with the oldest access history.

[Problem that the invention seeks to solve]

When dealing with a data management system that can generate indexes on multiple fields for one data record, it is common to repeatedly search with conditions on multiple indexed fields or store data records. The process is to repeatedly read the data page, read the upper index pages for the number of indexes, and read the lower index pages.

In such a case, the top index page is loaded every time a search or store is performed, and the lower index pages are also very likely to be reused. If there are no more buffers, all index pages will be released at the time of reading, and if there are fewer buffers, the buffers will not be used effectively and all page reads will be physical reads. The drawback is that the performance is very poor.

The present invention eliminates the drawbacks such as q, and aims to provide a method that can effectively utilize buffers and improve processing efficiency.

[Means for solving problems]

The present invention provides a buffer management method for a data management system that includes a buffer secured in memory and a file input/output means that reads page units from a file. A buffer management table that stores access history and buffer request level numbers, and if the requested page exists in the buffer management table, its address is returned; if it does not exist, the page with the highest level number in the buffer management table is returned. A buffer management table control means that releases a buffer containing a page with the oldest access history among large items and returns its address, and a buffer request level that indicates the page number to be read from the page requester and the degree of buffer request for the page. The present invention is characterized by comprising an input/output means for inputting a page number and returning an address from which a page has been read, and a control section for controlling the buffer management table control means, the input/output means, and the file input/output means. do.

[Effect]

The page number to be read from the page requester and the buffer request level number indicating the degree of buffer request for the page are input from the input/output means. The control unit passes the request page number and request level number to the buffer management table control means.

The buffer management table control means searches for the requested page from the buffer management table, and if it exists, returns its status and address to the control unit, and if it does not exist, selects the page with the oldest access history from among those with the highest level number. It searches for the page, releases the buffer for the found page, rewrites the page number and page request level, and returns a status indicating that the page does not exist and the address of the released buffer to the control unit.

The control unit receives these statuses and addresses, determines whether they exist on the buffer, returns the address to the input/output means if it exists, and sends the address and request to the file input/output means if it does not exist. Pass the page, read the specified page at the specified address, and return the address to the input/output means.

Thereby, the buffer can be used effectively and processing efficiency can be improved.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

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

In the figure, solid lines indicate the flow of control, and dashed lines indicate the flow of data.

The embodiment of the present invention includes a buffer 2 secured on memory,
A file 3, an input/output means 7 for inputting a page number to be read from a page requester and a buffer request level number indicating the degree of buffer request for the page, and returning the address from which the page is being read; Buffer management table 1 stores addresses, buffer access history, and buffer request level numbers, and if the requested page exists in buffer management table 1, the address is returned, and if it does not exist, it is stored in buffer management table 1. A buffer management table control means 4 that releases the buffer containing the page with the oldest access history among those with the largest level number and returns its address, and reads a specified page in the file to a specified address. File input/output means 6, buffer management table control means 4, input/output means 7, and file input/output means 6
A control section 5 is provided.

FIG. 2 is a configuration diagram of the buffer management table 1 according to the embodiment of the present invention, and the buffer management table 1 includes page numbers, page request level numbers, access history for pages, and addresses of buffers in which the corresponding pages are read. Consisted of.

Next, the control section 5 and the buffer management table control means 4
The processing will be explained below. FIG. 3 is a flowchart showing the processing procedure of the control unit 5 according to the embodiment of the present invention, and FIG. 4 is a flowchart showing the processing procedure of the buffer management table 4 according to the embodiment of the invention.

First, in FIG. 3, the control unit 5 inputs the requested page number and page request level from the page requester through the input/output means 7 in step 301. Next, in step 302, the requested page number and page request level are passed to the buffer management table control means 4, and then, in step 303, it is determined from the buffer management table control means 4 whether or not the requested page is on the buffer 2. Receives status and buffer address. Next, in step 304, it is determined whether or not the requested page is on buffer 2. If it is determined that the page is on buffer 2, control is transferred to step 306, and in step 306, the buffer management table control means 4
The receiver notifies the page requester of the received address through the input/output means 7, and ends the process.

Next, if it is determined in step 304 that the requested page is not on the buffer, control is transferred to step 305,
In this step 305, the address and page number of the buffer to be read are passed to the file input/output means 6, and the requested page is read from the file 3. Next, step 3
At step 06, the address received from the buffer management table control means 4 is notified to the page requester through the input/output means 7, and the process is terminated.

Next, as shown in FIG. 4, the buffer management table control means 4 receives the page number and page request level number from the control section 5 in step 401.

In step 402, the requested page is searched from the buffer management table 1. In step 403, it is determined whether or not the requested page exists on the buffer. If it is determined that the page exists, control is transferred to step 404, and step 40
In step 4, the step indicating that the page exists and its address are returned to the control unit 5, and the process ends.

If it is determined in step 403 that the page does not exist on the buffer, control is transferred to step 405.

In step 405, the buffer management table 1 is searched for the one with the oldest access history among those with the largest level number. In step 406, the page found in step 405 is targeted for release, and the page number and page request level in bath management table 1 are rewritten.

In step 407, the status indicating that the page does not exist and the address of the buffer released in step 406 are returned to the control unit 5, and the process ends.

〔Effect of the invention〕

As explained above, according to the present invention, in a data management system, when reading a page, it is possible to set the priority order of pages to be left in the buffer depending on whether the pages are higher in the index, lower pages, or data pages. , when conventional buffer management methods have a small number of buffers, even though they are read many times like the top index page, they are released many times because they are treated like other pages. This has the effect of eliminating the drawback that physical reading occurs every time a read is performed, which significantly reduces processing efficiency.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. FIG. 2 is a diagram showing an example of the structure of a buffer management table according to an embodiment of the present invention. FIG. 3 is a flowchart showing the processing procedure of the control unit according to the embodiment of the present invention. FIG. 4 is a flowchart showing the processing procedure of the management table control means according to the embodiment of the present invention. 1...Buffer management tabletop 2...Buffer, 3
... Finope 4... Buffer management table control means, 5... Control unit, 6... File input/output means, 7
...Input/output means. Patent Applicant NEC Corporation 9゜ Agent Patent Attorney Takashi Ide 1 Figure 1 Embodiment Example Buffer management table structure side Figure 2 Figure

Claims (1)

[Claims] 1. In a buffer management method of a data management system that includes a buffer secured in memory and a file input/output means that reads page units from a file, A buffer management table that stores addresses, buffer access history, and buffer request level numbers, and if the requested page exists in the buffer management table, the address is returned, and if it does not exist, the level A buffer management table control means that releases the buffer containing the page with the oldest access history among those with the largest number and returns its address, and the page number to be read from the page requester and the buffer request degree of the page. an input/output means for inputting a buffer request level number indicated and returning an address from which a page is read; and a control section for controlling the buffer management table control means, the input/output means, and the file input/output means. A buffer management method for a data management system characterized by the following.