In
database applications, terms such as DB, DBMS, and DBS are commonly used, and their forms are defined as follows.
Database (DataBase, DB for short)
Strictly speaking, a database is "a warehouse that organizes, stores, and manages data according to a data structure." The database can be shared by various users, has the characteristics of less redundancy, close connection between data, and high data independence.
Database Management System (DataBase Mangement System, DBMS for short)
Database management system (database management system) is a kind of software that manipulates and manages databases, used to establish, use and maintain databases, referred to as dbms. It conducts unified management and control of the database to ensure the security and integrity of the database. Users access data in the database through dbms, and database administrators also perform database maintenance through dbms. It allows multiple applications and users to use different methods to create, modify and query databases at the same time or at different times.
The database management system mainly provides the following functions.
1. Data definition: DBMS provides data definition language DDL (Data Definition Language) for users to define the three-level schema structure, two-level image, integrity constraints and confidentiality constraints of the database. DDL is mainly used to establish and modify the database structure of the database. The library structure described in 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 (Data Manipulation Language) for users to implement operations such as adding, deleting, updating, and querying data.
3. Database operation management: The operation management function of the database is the operation control and management function of the DBMS, including concurrency control in a multi-user environment, security check and access restriction control, integrity check and execution, and organization and management of operation logs , Transaction management and automatic recovery, that is, to ensure the atomicity of transactions. These functions ensure the normal operation of the database system.
4. Data organization, storage and management: DBMS should organize, store and manage all kinds of data, including data dictionary, user data, access path, etc. It is necessary to determine the file structure and access method to organize these at the storage level Data, how to realize the connection between data. The basic goal of data organization and storage is to improve the utilization of storage space, and to select appropriate access methods to improve access efficiency.
5. Database protection: The data in the database is a strategic resource of the information society, and the protection of the data is very important. The protection of the database by the DBMS is realized through four aspects: database recovery, database concurrency control, database integrity control, and database security control. Other protection functions of DBMS include system buffer management and some adaptive adjustment mechanisms for data storage.
6. Database maintenance: This part includes functions such as database data loading, conversion, dumping, database recombination and reconstruction, and performance monitoring. These functions are completed by each application program.
7. Communication: DBMS has related interfaces for online processing with operating system, time-sharing system and remote operation input, and is responsible for processing data transmission. For the database system under the network environment, it should also include the communication function between the DBMS and other software systems in the network and the interoperability function between the databases.
Database System (DataBase System, DBS for short)
The database system generally consists of 4 parts:
(1) Database (DB) refers to a collection of organized and shareable data stored in a computer for a long time. The data in the database is organized, described and stored according to a certain mathematical model, with less redundancy, higher data independence and easy scalability, and can be shared by various users.
(2) Hardware: various physical devices that constitute a computer system, including external devices required for storage. The hardware configuration should meet the needs of the entire database system.
(3) Software: including operating system, database management system and application programs. The database management system (DBMS) is the core software of the database system. It works under the support of operating systems (such as Windows, Linux and other operating systems) to solve how to organize and store data scientifically, and how to efficiently obtain and maintain data System software. Its main functions include: data definition function, data manipulation function, database operation management and database establishment and maintenance.
(4) Personnel: There are mainly 4 categories.
The first category is system analysts and database designers: system analysts are responsible for the analysis and specification of application systems. They work with users and database administrators to determine the hardware configuration of the system and participate in the outline design of the database system. The database designer is responsible for the determination of the data in the database and the design of all levels of the database model.
The second category is application programmers, responsible for writing applications that use databases. These applications can retrieve, create, delete or modify data.
The third category is end users, who use the system interface or query language to access the database.
The fourth type of user is the database administrator (data base administrator, DBA), responsible for the overall information control of the database. The specific responsibilities of the DBA include: the content and structure of the information in the specific database, determine the storage structure and access strategy of the database, define the security requirements and integrity constraints of the database, monitor the use and operation of the database, and be responsible for the performance improvement of the database. Reorganization and reconstruction of the database to improve system performance.
