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Database system
This refers to a system composed of a group of related files.
File
This is a group of records of the same type.
Record
This refers to a group of related fields e.g. a student record may be composed of fields such as
student name, student number, course, date of birth, etc
Database management system
This refers to a complex software system that constructs, expands and maintains the database.
It also provides the controlled interface between the user and data in the database.
(i) Features of a DBMS that provide data security and integrity:
1.Usernames and passwords- used to prevent unauthorized
2.Transaction locks i.e. write locks and read locks. Write locks prevent other
processes(programs) from updating data currently being updated by a process. Read locks
prevent any other processes from updating data that is currently being read by a process.
3.Checkpoints and journals. A checkpoint is a ?snapshot? of the database
before it wasupdated by processes/programs and the journal holds details of updates
subsequently made. In the event of failure, the recovery process can rebuild the database
from checkpoints and journals.
4.User rights and privileges- access to files or fields of records could be
granteddepending on the user privileges.
5.Encryption- coding of data by special algorithm that renders them unreadable
withoutdecryption.
Integrity checks e.g. checks on relationships amongst tables to ensure that they are
validand data validations
(ii) Data redundancy
This refers to the presence of duplicate data in multiple data files. Data redundancy occurs
when different divisions, functional areas, and groups in an organization independently
collect the same piece of information. For instance, within the commercial loans division of a
bank, the marketing and credit information functions might collect the same customer
information contained in separate files.
Problems caused by data redundancies:
1.Large storage space requirements
Since each functional area of an organization maintains the same piece of information,
the resource requirements (hard disk, optical disk, magnetic tape) may be very large.
2.Problem of securing all the redundant data
Though the data in such a database is redundant, it must still be secured from
unauthorized access. This task is very difficult to implement because each functional area
of an organization holds the data.
3.Confusion
Since data is collected and maintained in so many different places, the same data may
have different meanings in different parts of an organization. Simple data items such as
the fiscal year, employee identification, and product code can take on different meanings
as programmers and analysts work in isolation on different applications.
4.Difficulty in performing updates
To update a redundant data item, one must update all instances of the redundant item in
all the department files of an organization. This is clearly hectic!
5.Compromised system integrity
In cases where only one instance of a redundant data item is updated, the system integrity
is compromised since the other instances of the redundant data item in the rest of the
organization‘s departments will differ from the updated instance of the redundant data
item.
(iii) Precautions that should be taken into account in establishing a centralized data control
system to avoid redundancy:
1. One should ensure that adequate security mechanisms are in place to ensure that users are
granted access to only what they are supposed to access.
2.One should ensure that the system is fault tolerant i.e. it should be not too centralized as to
be vulnerable to failure.
gregorymasila answered the question on November 21, 2017 at 20:19
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