Describe the main components in a DBMS.

What will be an ideal response?

The major software components in a DBMS environment are depicted in Figure 3.20. The main
components in a DBMS are:
? Query processor. This is a major DBMS component that transforms queries into a series of
low-level instructions directed to the database manager.
? Database manager (DM). The DM interfaces with user-submitted application programs and
queries. The DM accepts queries and examines the external and conceptual schemas to
determine what conceptual records are required to satisfy the request. The DM then places a
call to the file manager to perform the request.
? File manager. The file manager manipulates the underlying storage files and manages the
allocation of storage space on disk. It establishes and maintains the list of structures and
indexes defined in the internal schema. If hashed files are used, it calls on the hashing
functions to generate record addresses. However, the file manager does not directly manage
the physical input and output of data. Rather, it passes the requests on to the appropriate
access methods, which either read data from or write data into the system buffer (or cache).
? DML preprocessor. This module converts DML statements embedded in an application
program into standard function calls in the host language. The DML preprocessor must
interact with the query processor to generate the appropriate code.
? DDL compiler. The DDL compiler converts DDL statements into a set of tables containing
metadata. These tables are then stored in the system catalog while control information is
stored in data file headers.
? Catalog manager. The catalog manager manages access to and maintains the system catalog.
The system catalog is accessed by most DBMS components.