Page 11 - DCAP402_DCAO204_DATABASE MANAGEMENT SYSTEM_MANAGING DATABASE

Database Management Systems/Managing Database

Notes It means that without a DBMS, the data will simply be dumped into one or more files. For any
updation, the files need to be opened and manually search for the line or record, update and then
save the file. Now you can understand the difficulties involved in marinating this type of
information storage.

Figure 1.2: Database Approach

Application program -1
with data semantics Description
Manipulation
Application program -2 Control
with data semantics Database
........
Application program -3
with data semantics

With the advent of database systems, the file processing approach is no longer used. Now you
can observe with the Figure 1.2 that the database is in the disk which in turn is controlled by the
DBMS. In this approach the Application Program-1 along with its data semantics, Application
Program-2 along with its data semantics, etc., interact with the database where the actual data
and constraints are stored through the DBMS. The DBMS provides the necessary control and
manipulation software modules for these application programs to access the data stored in the
database.
This way the applications are free from the system dependent code and achieve program-data
independence.

Task Find out the various sources of database management system.
Drawbacks of File Processing System

1. Catalog: In DBMS, the database structure is stored in a catalog and it also contains the
storage details with constraints.
The DMBS software must equally work with any number of database applications provided
the catalog contains the structure and other details of that application. In file processing
the data definition is part of the application program.

Example: Record declaration in Pascal.
Class or structure declaration in C++.
2. Program-data independence: In file processing, if changes are done in the structure of the
file, then we may require changing the program design that accesses it. In DBMS the access
programs are written independent of any specific files. This is called as program-data
independence.
The DBMS stores the data in such a way that the user need not be aware of these details.
This concept is called as data abstraction and it may also be called as conceptual
representation.

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