At all times, any organization needed to store, disseminate and process information. The totality of resources that allow you to do this within an organization is called an information system, and the DBMS is an integral part of it. The life cycle of a database is inextricably linked with the life cycle of an information system. It consists of the following stages: planning and developing a database, formulating requirements for the system, collecting and analyzing user requirements, designing a database, developing application programs, creating prototypes, implementing, converting and loading data, testing, operating and maintaining. Some steps may be omitted. It is depending on the size of the project.
With the development of accessible technologies, methods for storing and managing data have been developed that are used in information systems of organizations from file cabinets to modern DBMS of client-server architecture. Briefly, their evolution can be described as follows: manual file cabinets – file systems – modern DBMS.
The first manual file cabinets archaeologists date around 3300 - 3000 years BC. These were clay tablets collected in boxes. These databases belong to the Sumerian civilization, which flourished in southern Mesopotamia between the Tigris and Euphrates rivers in modern Iraq. So today the databases are more than 5000 years old. You will be surprised, but the principle of the operation of manual file cabinets has not changed since then. They still cope with the processing of information for cases where it is only necessary to store and retrieve a relatively large amount of data. However, if you need to establish cross-links between data or process any information, then manual file cabinets will be ineffective.
The beginning of the computer era of databases can be considered 1968, when the use of the first file system “George 3” began. Notice how short the time span between 1968 and today is compared to more than 5,000 years of database history. But file systems were just the first attempt to computerize handheld file cabinets known to all. At the same time, a decentralized approach to data storage and processing was used. This means that within the organization, each department involved data processing specialists to work with information within the department. This led to great difficulties in obtaining an objective picture of the results of the work of the whole organization. In more detail, the disadvantages of file systems for storing and processing data are given in the lecture.
These difficulties have led to the standardization of sets of logically related data and their descriptions for sharing. So the first databases appeared, which are also called a set of integrated records with self-description. From that moment on, a number of terms describing the structure of databases become generally accepted: a description of the data is called a system catalog or a data dictionary, and description elements themselves are called meta-data, that is, " data about data. " It is the existence of data self-description that ensures independence between application programs and data (program-data independents).
The next step was the standardization of language and software tools for creating, maintaining and sharing a database by many users. Such a collection is now customarily called a database management system (DBMS). It consists of a server, clients, and business rules. You can briefly describe the interactions of the listed parts of the DBMS: the server processes requests of clients in accordance with business rules. See the lecture for more details.
The position of the parts of the DBMS relative to each other defines its architecture. The first solution was the file server architecture. In fact, this is the placement of the database and application programs (server and client applications) involved in its processing on a computer that is accessible to all interested users of the organization. Thus, all clients got access to data through a single user interface from their personal computers. Storage of data processing applications on computers of clients is not widespread because there was much difficulties of such systems service. For instance when changing the version of the client application, it was necessary to change it in a large number of workplaces.
The weaknesses of the file-server architecture of DBMS became the impetus for the creation and development of the client-server architecture of DBMS. Unlike the file-server architecture of DBMS, it does not provide direct access client’s applications to the database. There are two-tier and three-tier models of client-server architecture. The interaction of the database server and the client application is described in the lecture.
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