Database Management System

Topic Outline

  • Database Management System
  • Data Dictionary
  • File Maintenance and Retrieval
  • Database Security
  • Database Security Threats
  • Backup and Recover the Database

Database Management System

It is a collection of programs that use to create, update and maintain a database. DBMS provides the following facilities.

  • To store the data on a storage medium.
  • To insert, update, delete and retrieve particular data for reports.
  • To define the structure of the database.
  • User can specify the format, data types, and rules for data to be stored in a database.

Data Dictionary

The data dictionary is also called a repository. It contains data about data. So it is called metadata. The data dictionary contains data about users and programs. It also contains data about each file and field in these files in the database. Each file stores data such as file name, number of records in the file, description of the file, and relationship of file with other files. Field stores data such as field name, field type, size, validation rules, description, and relationship of fields with other fields. Data dictionaries also store the details such as who the user accessed the database and when he accessed it. It is also used to specify the default value. 

  • Default Value

A value that is initially shown in a field is called a default value. 

File Maintenance and Retrieval 

The database management system provides a tool to retrieve and maintain data.

  • Queries

It is used to retrieve data from the database query is written in database access language. Retrieve data from the database and show it in the form of a table.


Roll no 

Name 

Marks 

Grade 

1 

Ali 

990 

A+ 

2 

Subhan

995 

A+ 

3 

Usman 

809 

B 

4 

Abdullah 

906 

A 

Example

The user executes a query to retrieve the record of a student who gets more than 900 marks. The query will show the following table as result.

Roll no 

Name 

Marks 

Grade 

1 

Ali 

990 

A+ 

2 

Subhan 

995 

A+ 

4 

Abdullah 

906 

A 

  • Query Languages

It provides a statement to manipulate data in the database. Statements are written in English-like language, that is easy to use. DBMS provides the facility of the wizard to create a query.

  •  Query by Example

It is used to retrieve data from a database without learning query language.

  •  Forms

The graphical user interface is used to interact with the ith database is called form. It is used to enter data into the database. Users can retrieve and update data in forms. The form consists of tables, buttons, and text boxes.

  • Forms are easy to use.
  • Forms use graphical interface.

  • Reports

It is the output of a database application. By manipulating the database user can generate different types of reports. Information is arranged in different ways. Reports contain charts and tables etc. Reports are important in making decisions. It provides quick results from the database. It can be printed easily. It can display data by using charts and graphs.

Database Security

It is a process of protecting the database from accidental threats or unauthorized access. The purpose of security is to reduce losses that may occur due to different security threats. The database is an important resource of any organization. 

  • Threat

It affects the database environment and the entire organization. The threat does not change the data in the database.


Database Security Threats

It is a situation that may affect a system intentionally or unintentionally. A threat may be a result of an event that involves a person harming the system. It results in intangible damage such as loss of software and hardware etc and also results in intangible damage such as customer confidence etc. 

Measures against Threats

Measures can be taken against database security threats. Some measures are as follows.

  • Authentication

It is the process of determining the identity of the user. The user has a unique identifier that is used to identify the user. Modern techniques that are used for authentication such as voice recognition, fingerprints, etc. 

  • Authorization

It is a process of granting the right to access a system. Authorization controls can be built into the software. Authorization controls are also known as access controls.

  • Views

It is a virtual table. It provides powerful security by hiding the parts of the database from unauthorized users. The user is not aware of the existence of any attributes.

  • Backup and Recovery

It is a process of taking a copy of the database as a backup. The recovers over the backup in case of system failure. A logfile is used to recover data. 

  • Integrity

It is used to maintain a secure database system. Constraints are used to prevent data from becoming invalid. 

  • Encryption

Encryption becomes important if the database contains sensitive data. The database management system provides an encryption facility to secure data. It is a process of encoding data by a specific algorithm. Many techniques are used for encrypting data.

Backup and recover the database

A database can be damaged due to different reasons such as software problems, hardware problems, human error, etc. To restore the database some techniques are used that are as follows.

  • Backup

The database management system provides a facility for the backup of the database. Some database management system provides a built-in backup facility.

  • Log

It is a list of activities that change the content of the f database. If the user changes the phone number of a student, the database management system stores the following in the log:

  • A copy f the student record before the change.
  • The actual change of phone number data.
  • A copy of the student record after the change.

  • Recovery

The database management system also provides the facility to recover the database. Rollback and Roll forward techniques are used to restore the database.

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