Overall Database Structure (Database Components) | Database Management System

Overall Database Structure (Database Components) | Database Management System

Overall Database Structure (Database Components) : The following figure illustrates main components of a typical DBMS:

 

DDL Compiler: The DDL statements are sent to DDL compiler, which converts these statements to set of tables. These table contains the metadata concerning the database and are in the form that can be used by other components of the DBMS.

DML Pre-compiler and Query Processor: The DML pre-Compiler converts he DML statements embedded in an application program to normal procedure calls in the host language. If the DML statements include the queries then it goes to query processor, which interprets the Ouery and converts it into an efficient series of operations. The query processor components include:

DDL interpreter: Which interprets DDL statements and records the definition in the data dictionary.

DML compiler : Which translates DML statements in the query language into an evaluation plan consisting of low-level instructions that the query evaluation engine understands. The DML Compiler also performs query optimization, i.e., it pick the lowest cost evaluation from among the alternatives.

Query Evaluation Engine: which executes low-level instructions generated by the DML compiler,

Data Managers: Data manager control the database. It provides the interface between the database and the application programs. Data manager convert the user’s request coming directly via the query processor or via application programs to a physical file system. The data manager is responsible for interaction with the file manager, integrity and security enforcement and concurrency control.

File Manager: File manager is responsible for allocation of space on the disk storage and the data structures used to represent information stored on physical media.

Data Files: These are actual physical files which contain the data.

Data Dictionary: is used to store the metadata about the structure of the database. It also keeps track of relationships that exist between various data structures.

Telecommunication System : A modern client server is implemented through a sophisticated network. It includes transmission media, servers, routers, Switches etc.

Access aids: Such as indexes which provide fast access to data items.