What is the data dictionary in DBMS
Database management system (DBMS) explained
Function / requirement
Storage of data
Databases store electronic texts, documents, passwords and other information that can be accessed through queries.
Revision of data
Most databases allow - depending on the access rights - stored information to be edited directly.
Deletion of data
Data records contained in databases can be completely deleted. In some cases, deleted data can be recovered, in others the information is lost forever.
Management of the metadata
Information is usually stored in databases with metadata or meta tags. These create order within the database and make z. B. a search function possible. Access rights are also often regulated via metadata.
Data management follows four fundamental operations: Create, Read / Retrieve, Update and Delete. This concept, known as the CRUD principle, is the basis for data management.
Databases must be secure so that unauthorized persons cannot access the stored data. In addition to a powerful encryption method, careful management, especially by the main administrator, is essential for data security. Data security usually means taking the technical precautions to prevent manipulation or loss of data. It is therefore a core concept of data protection.
Data integrity means that data within a database adhere to certain rules so that the correctness of the data is ensured and the business logic of the database is defined. This is the only way to ensure that the database as a whole functions constantly and consistently. There are four of these rules in relational database models: realm integrity, entity integrity, referential integrity, and logical consistency.
Database applications allow access to the database from various devices. In multi-user operation, the distribution of rights and data security are elementary. Another challenge for databases in multi-user operation is how to keep data consistent with simultaneous read and write access by many users without impairing performance too much.
On the technical side, a database must be able to process every query as optimally as possible in order to guarantee good performance. If a database goes "too many ways" with a data query, the overall performance of the database system suffers.
Triggers and Stored Procedures
These procedures are mini-applications stored within a database management system that are called up (“triggered”) when certain change actions are taken. This means, inter alia. achieved an improvement in data integrity. Database triggers and stored procedures are typical processes in relational databases - the latter can also contribute to system security if users are only allowed to carry out actions with ready-made procedures.
System transparency is particularly relevant in distributed systems: By withholding data distribution and implementation from the user, the use of the distributed database is then similar to that of a centralized database. Various levels of system transparency reveal or obscure the background processes. The main function, however, is to simplify the use as much as possible.
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