Page 102 - DCAP516_COMPUTER_SECURITY

Computer Security

Notes state. For example, an amount of ` 50 has to be transferred from account A to account B.
The amount has been debited from account A but have not been credited to account B and
in the meantime, some failure occurred. So, it will lead to an inconsistent state. So, we
have to adopt a mechanism which ensures that either full transaction should be executed
or no transaction should be executed i.e. the fund transfer should be atomic.
6. Concurrent Access Problems: Many systems allow multiple users to update the data
simultaneously. It can also lead the data in an inconsistent state. Suppose a bank account
contains a balance of ` 500 and two customers want to withdraw ` 100 and ` 50
simultaneously. Both the transactions are reads from the old balance and withdrawal
from that old balance will show ` 450 and 400 which is incorrect.
7. Security Problems: All the users of database should not be able to access all the data. For
example, a payroll personnel needs to access only that part of data which has information
about various employees and is not needed to access information about customer accounts.
Files may contain duplicate records. Therefore, they are susceptible to a loss of integrity if
all files are not updated at the same time. Programs are bound to a file. If a file structure is
modified then all programs that access it need to be modified. Thus, alterations to file
structures are difficult and expensive.
Database systems originated in the late 1950s and early 1960s largely by research and development
of IBM Corporation. Most developments were responses to needs of business, military,
government and educational institutions, which are complex organisations with complex data
and information needs.

Self Assessment

Fill in the blanks:
1. A field or item of data is one or more bytes that contain data about an ……………….. of an
entity in the information system.
2. An ………………. in a payroll system is an individual employee.
3. A …………………….. is a collection of fields relating to a specific entity.
4. With a………………………………………, records must be read in the same order as they
were written to the storage media.
5. The term……………………………… System, relates to an assembly of those steps in logical
order.
6. Examples of ………………………………. processing include generation of mark-sheets of
students.
8.11 Database Management Systems (DBMS)

This is the interface between the users (application programmers) and the database (the data).
A database is a collection of data that represents important objects in a user’s business. A database
management system (DBMS) is a program that allows users to define, manipulate, and process
the data in a database in order to produce meaningful information.

DBMS is collection of programs that enables you to store, modify, and extract important
information from a database. There are many different types of DBMS, ranging from small
systems that run on personal computers to huge systems that run on mainframes.

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