The components of DBMS are the following :
1. DDL Compiler : DDL compiler processes schema definitions, specified in the DDL, and, stores description of the schemas in the DBMS catalogue. The catalogue includes information as the name of file, data items, mapping information among schemas and constraints.
2. Run-time database processor : It handles database accesses at run time; it receives retrieval or update operations on the database. The query compiler handles high-level queries that are entered interactively.
3. Pre-compiler : The pre compiler extracts DML commands from an application program written in a host programming language. These commands are sent to the DML compiler for compilation into object code for database access.