Databases 11.1. The concept of a database. Database Management Systems

The word “data” is defined as the dialectic component of information in the form of registered signals. Data registration can be carried out by any physical method (mechanical movement of physical bodies, changing their shape or surface quality parameters, changing electrical, magnetic, optical characteristics, chemical composition or nature of chemical bonds, changing the state of the electronic system, etc.). Initially, the following data types were used when creating databases:

1) numeric (for example, 17; 0.27; 2E-7);

2) character or alphanumeric (in particular, "ceiling", "table");

3) dates that are set using a special type of "Date" or as ordinary character data (for example, February 12, 2005, 12/02/2005).

Other types of data were later identified, including:

1) temporary and date-temporary, which are used to store information about the time and / or date (for example, February 5, 2005, 7:27:04, February 23, 2005, 16:00);

2) variable-length character data for storing textual information of great length;

3) binary, which are used to store graphic objects, audio and video information, spatial, chronological and other special information;

4) hyperlinks that allow you to store links to various resources located outside the database.

A database is a collection of interrelated data that is stored in a computer memory for displaying the structure of objects and their connections in the studied domain. It is the main form of organizing data storage in information systems.

The database management system is a complex of symbolic and software tools designed to create, maintain and organize joint access to databases of many users.

The first DBMSs were developed by IBM - IMS (1968) and Software AG – ADABA • (1969). At the moment there are a large number of different database management systems (more than a few thousand), and their number is constantly growing.

Among the main functions of the DBMS (functions of the highest level) can be identified storage, modification and processing of information, as well as the development and receipt of various output documents.

The functions of a lower level DBMS include:

1) data management in external memory;

2) buffer management OP;

3) transaction management;

4) logging of changes in the database;

5) ensuring the integrity and security of databases.