DBMS Elements




1)      DDL (Data definition language): DBMS provide a facility known as DDL which can use to define the concept of schema. It also give some details about how to implement this schema in physical device used to stored data. This definition includes all the entity sets and their relation among the entity set. The definition also including the constraints that have to be maintain including the constraint on that have to be maintain including the constraints on the values assign to different attributes in a same or different record. These definition can be describe meta data about the data in the data base are expressed in DDL of DBMS and maintain in a complied form the complied form of definition are known as data dictionary or system catalog.


2)      DML(Data manipulation language): DML is a language that access or manipulated as organized by appropriate data model. Data manipulation includes retrieval of data insertion of data deletion or modification of exiting data base. DML also support query language DML provides command to select and retrieved data form database command are liked UPDATE, INSERT, DELETE, etc.


3)      DML Pre Compiler: the convert DML statement in an application program to normal procedural call in the host language the precompiled must interact with query processor in order to generate the appropriate code.


4)      DDL Compiler: the convert’s data definition statement into a set of table these table contains information related to data based and are in the form that can be used by other component of database management system.

5)      File Manager: it manages the allocation of space on disk storage and the data structure used to represent information stored in disk the file manager can be implemented using an interface to the exist file system proved the operating system to host computer or it can include a file sub system written specially for DBMS.

6) Data Base manager: it is a program which provides the interface between the low level data. Stored in data base and the application program and queries submitted to the system. One of the functions of data base manager is to convert the user query coming directly through the query processor or indirectly to the application program.







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