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Functions of DBMS:

A DBMS performs several important functions of the database. Most of these functions are transparent to end users, and most can be achieved only through the use of a DBMS. They include the following functions.

1.       Data Dictionary Management: The DBMS stores Metadata (i.e. definitions of the data elements) in a data dictionary. All the programs that access the data in the database work through the DBMS. The DBMS uses the data dictionary to look up the required data component structures and relationships. Additionally, any changes made in a database structure are automati­cally recorded in the data dictionary. Thus, the DBMS provides data abstraction, and it removes structural and data dependency from the system.  

2.       Data storage management: The DBMS creates and manages the complex structures required for data storage. A modern DBMS provides storage not only for the data, but also for related data-entry forms or reports, data validation rules, code, structures to handle video and picture formats, and so on. Data storage management is also im­portant for database performance tuning. The DBMS actually stores the database in multiple physical data files.  

3.       Security management: The DBMS creates a security system that enforces security and data privacy. Security rules determine which users can access the database, which data items users can access, and which data operations (read, add, delete, or modify) the user can perform. This is especially important in multiuser database systems.  

4.       Multiuser access control: The DBMS uses complex algorithms to ensure that multiple users can access the database concurrently without compromising the integrity of the database.  

5.       Backup and recovery management: The DBMS provides backup and data recovery to ensure data safety and integrity. Current DBMS systems provide special utilities that allow the DBA perform routine and special backup and restore procedures.  

6.       Data integrity management: The DBMS promotes and enforces integrity rules, thus minimizing data redundancy and maximizing data consistency. The data relationships stored in the data dictionary are used to enforce data integrity.  

7.       Database access languages and application programming interfaces: The DBMS provides data access through a query language. A query language is a nonprocedural language, which allows the user to specify what must be done without having to specify how it is to be done. The DBMS also provides application programming interfaces to languages such as C, Java, Visual Basic, and etc. 

8.       Database communication interfaces: Current-generation DBMSs accept end-user requests via multiple, different network environments. For example, the DBMS might provide access to the database via the Internet through browsers. In this environment, communications can be accomplished in different ways.
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