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WHAT IS A SYSTEM BD? Persistent Data

WHAT IS A SYSTEM BD?

is a system for computer files, that is, is a computerized system whose purpose gral. Is to maintain information and make it available upon request.	DATA
	ARCHIVES	RECORDS	FIELDS

difference between data (values \u200b\u200bstored in the database) and information (referred to the meaning of these values \u200b\u200bfrom the point of view of a user).

RELATING TO AN ORGANIZATION, WE DETECTING PHYSICAL AND ABSTRACT COMPANIES (BANK ACCOUNT) AND YOU WILL BE RELEVANT TO THE ORGANIZATION THAT WILL BE STORED IN A PHYSICAL TO BE USED BY CERTAIN PEOPLE (INTEREST).

4 Components of a system of BD

SYSTEM BD	DATA OR INFORMATION	SHARED
		INTEGRATED
	HARDWARE OR EQUIPMENT
	SOFTWARE OR PROGRAMS	DBMS
		APPLICATION PROGRAMS
		TOOLS
	USERS

1 - INFORMATION

Multiple users can access the database at the same time, the goal is to ensure that each individual can behave as if you were working with a single user system.

should assume that all data stored in the system are kept in a single database. But in practice there may be reasons, even in small systems, to deliver information in several different databases.

The information in the database will be integrated and shared.

· Integrated : the BD can be considered as a unification of multiple data files, otherwise different, and eliminates of all or part of any redundancy between them.

· Shared: more than 1 user accesses the same data simultaneously (concurrent access or not.)

Another consequence of the fact (the integration of the database) is that usually a particular user only deal with a subset of the total database. Different users receive the database in several different ways. In fact, even when 2 users share the same subset of the database, how can see that subset significantly differ in the details.

2 - TEAM

Computers, storage, network volumes or unique to a disc.

components consisting of system equipment are

· The secondary storage volumes where stored data is preserved along with the devices I / S associated device drivers, channels of I / S, and others.

· The processor or processors and main memory associated that make possible the implementation of programs of BD.

3 - PROGRAMS

a) Among the BD physics itself and users of the system there is a level programs, the BD management system (DBMS) . The DBMS manages all requests access to the database made by the users, as well as the addition or deletion of files (tables), obtaining and updating data from those files. One of the general functions is alienate users BD details team level.

The DBMS provides users a view of the BD at a level well above the level of equipment, and makes possible its operations is an important component software but not the only (utilities, report generators, tools to develop applications).

Software consists of a set of modules, interfaces users see the data of physical media. Stored in : a data file, index files that allow faster access to stored files. By direct access pointers. And also a data dictionary containing information on the structure of data files, data type logical, Boolean, size ... (the database engine).

The DBMS is definitely the most important software component of the entire system, but not alone. among others may be mentioned the utilities, tools to develop applications for design aid, report generators, etc.

b) application programs : for a user to access data.

c) Tools : p / generate reports, forms, p / programmers and some who know a little more.

4 - USER

are taken into account three classes of users (people who interact with the system):

· Application Developer: will write application programs using the database. These programs operate on data in all the usual ways: retrieving, inserting, modifying or deleting data. It takes place appropriate requests to the DBMS. Generating applications for other users with minimal knowledge entering.

· End User: who interacts with the system from an online terminal, can access the database through an online application above, or use an interface included as an integral part of the BD system programs. (Eg SQL).

ü INGENUOUS: screen and nothing else.

ü SOPHISTICATED: data query, knows a little more, application programs.

ü SPECIALIZED: tools with images ...

Most systems also include additional integrated interfaces with which the user does not need to issue explicit commands like SELECT , but function by choosing options from a menu or a filling form. These interfaces are often easier to use for people with no formal studies of data processing. The interfaces handled by commands (such as query languages) tend to require some knowledge of data processing.

· BD Manager (DBA): Person centralizes responsibility and control of the database. Technician responsible for implementing the decisions of the Data Manager. Works together with the DA, is not considered a user, who designed the system, management position, knows the needs of the user, but is implemented by the DBA. Is a professional data processing. Your task is to create the database itself and enforce technical controls needed to support the policies dictated by the data administrator. It is also responsible for ensuring the proper functioning of the system and providing other related services of a technical nature.

orders to the system, MANAGER) DA's policy DBA (maintains contact with all users, TECHNICAL)