1. Data definition: The DBMS provides data definition language DDL (Language) for user-defined three-level schema structures, two-level images, and integrity constraints and confidentiality restrictions. DDL is mainly used to establish and modify the database structure. The library structure described by DDL only gives the framework of the database, and the framework information of the database is stored in the data Dictionary. 2. Data manipulation: DBMS provides data manipulation language DML (manipulation Language) for users to implement data append, delete, update, query and other operations. 3. Database operation Management: Database operation management function is DBMS's operation control, management function, including concurrency control in multiuser environment, security check and access limit control, integrity check and execution, organization management of running log, transaction management and automatic recovery, that is to guarantee the atomicity of transaction. These functions ensure the normal operation of the database system. 4. Data organization, storage and management: DBMS to classify and organize, store and manage various kinds of data, including data dictionary, user data, access path and so on, need to determine what file structure and access way to organize the data at the storage level, how to realize the connection between data. The basic goal of data organization and storage is to improve storage space utilization and choose appropriate access method to improve access efficiency. 5. Database protection: Data in the database is the strategic resource of the information society, so the protection of data is of paramount importance. The DBMS protects the database through 4 aspects: Database recovery, database concurrency control, database integrity control, database security control. Other protection functions of DBMS include the management of system buffers and some adaptive regulation mechanism of data storage. 6. Maintenance of the database: This section includes data loading, conversion, dump of database, reconfiguration of database and performance monitoring functions, which are completed by various use programs respectively. 7. Communication: DBMS with the operating system online processing, time-sharing system and remote job input related interface, responsible for processing data transmission. The database system in the network environment should also include the communication function between DBMS and other software systems in the network, and the interoperability function between the databases.
DBMS main functions
