Hitachi, Ltd.

Hitachi Software Engineering Company, Ltd.

Hitachi Microcomputer Engineering, Ltd.

Toshio Honma

Masashi Tsuchida

Kazuhiko Ohmachi

Yasuhiro Imai

Yukio Nakano

Nobuo Kawamura

Hiroyuki Kitajima

Kiyoshi Yata

Tadashi Ohsone

Hideo Mutoh

Naohumi Sakai

Shoo Urabe

Nobuhiro Taniquchi

In a data base processing method including a central processing unit for analyzing a plurality of queries made from a plurality of users so as to determine an internal processing procedure with respect to a data base, and for performing the internal processing procedure; a secondary storage for storing data capable of being shared by each user; and, an input/output controlling processing unit including at least one cache storage, for controlling a transfer of a plurality of records which are required for input/output processing operations between the central processing unit and secondary storage. The data base processing method is featured in that a decision is made whether or not a prefetching operation is carried out at a start of an input/output processing operation by judging the internal processing procedure which has been formed by the query; a retrieval range into which a record to be fetched has been stored is formed when the prefetching operation is performed; and, a prefetching record number is determined as an input/output processing demand unit, taking account of an access characteristic of the internal processing procedure and also a system characteristic containing a size of the cache storage, a performance, of the central processing unit, and a traffic of the input/output processing unit.

Method apparatus for determining prefetch operating for a data base

With respect to input/output requests; a microprogram controls collection of data according to the data format; data accessing divides the requests for every recording medium and performs asynchronous processing; an on-line process is carried out in view of the processing priority order of the requests; parallel accessing sets requests for each medium; buffer control assures a block buffer and a page address list before receiving requests; data accessing sets a list of CCHHR codes in response to a continuous characteristic of the stored state in the recording medium; and mode deciding judges the two data transfer modes, a page search mode and a data search mode, in response to the requests.

Input/output processing method in a database management system

After passing through the process in which the number of one page I/O requests generated in a certain unit time period, the number of multiple pages I/O requests, and the number of pages required at each of the multiple pages I/O request are input, the quantity of the I/O requests generated in the above-described unit time period is calculated in accordance with the thus-input values. The unit (the number of pages) for a multiple pages I/O actually performed by one time operation of the I/O control device corresponding to the multiple pages I/O request from users is determined in accordance with the user's instruction or specific criterion for the system based on the result of the above-described calculation, the performance of the CPU, the performance of the I/O control device, the performance of the DASD (Direct Access Storage Decive), and to which DASD each of I/O requests corresponds. The result of this determination is employed as the unit (the number of pages) for the multiple pages I/O performed by one time operation of the I/O control device. In case of the specific criterion for the system, the structure may be constituted in such a manner that it can be automatically changed in accordance with the state of change in the quantity of the I/O request.

Data I/O transaction method and system

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Yokohama, Japan

Toshio Honma