Database Management Systems:Introduction and brief history to Database,Characteristics of database,Difference between File System & DBMS.,Advantages of DBMS,Functions of DBMS,Role of Database Administrator and Simplified Database System Environment.

Introduction to Database

1.1 Introduction

Database is a collection of related data. Database management system is software designed to assist the maintenance and utilization of large scale collection of data. DBMS came into existence in 1960 by Charles. Integrated data store which is also called as the first general purpose DBMS. Again in 1960 IBM brought IMS-Information management system. In 1970 Edgor Codd at IBM came with new database called RDBMS. In 1980 then came SQL Architecture- Structure Query Language. In 1980 to 1990 there were advances in DBMS e.g. DB2, ORACLE.

Data

• Data is raw fact or figures or entity.

• When activities in the organization takes place, the effect of these activities need to be recorded which is known as Data.

Information

• Processed data is called information

• The purpose of data processing is to generate the information required for carrying out the business activities.

In general data management consists of following tasks

• Data capture: Which is the task associated with gathering the data as and when they originate.

• Data classification: Captured data has to be classified based on the nature and intended usage.

• Data storage: The segregated data has to be stored properly.

• Data arranging: It is very important to arrange the data properly

• Data retrieval: Data will be required frequently for further processing,

Hence it is very important to create some indexes so that data can be retrieved easily.

• Data maintenance: Maintenance is the task concerned with keeping the data up- to-date.

• Data Verification: Before storing the data it must be verified for any error.

• Data Coding: Data will be coded for easy reference.

• Data Editing: Editing means re-arranging the data or modifying the data for presentation.

• Data transcription: This is the activity where the data is converted from one form into another.

• Data transmission: This is a function where data is forwarded to the place where it would be used further.

Metadata (meta data, or sometimes meta information) is "data about data", of any sort in any media. An item of metadata may describe a collection of data including multiple content items and hierarchical levels, for example a database schema. In data processing, metadata is definitional data that provides information about or documentation of other data managed within an application or environment. The term should be used with caution as all data is about something, and is therefore metadata.

Database

• Database may be defined in simple terms as a collection of data

• A database is a collection of related data.

• The database can be of any size and of varying complexity.

• A database may be generated and maintained manually or it may be computerized.

Database Management System

• A Database Management System (DBMS) is a collection of program that enables user to create and maintain a database.

• The DBMS is hence a general purpose software system that facilitates the process of defining constructing and manipulating database for various applications.

1.2 Characteristics of DBMS

• To incorporate the requirements of the organization, system should be designed for easy maintenance.

• Information systems should allow interactive access to data to obtain new information without writing fresh programs.

• System should be designed to co-relate different data to meet new requirements.

• An independent central repository, which gives information and meaning of available data is required.

• Integrated database will help in understanding the inter-relationships between data stored in different applications.

• The stored data should be made available for access by different users simultaneously.

• Automatic recovery feature has to be provided to overcome the problems with processing system failure.

DBMS Utilities

• A data loading utility:

Which allows easy loading of data from the external format without writing programs.

• A backup utility:

Which allows to make copies of the database periodically to help in cases of crashes and disasters.

• Recovery utility:

Which allows to reconstruct the correct state of database from the backup and history of transactions.

• Monitoring tools:

Which monitors the performance so that internal schema can be changed and database access can be optimized.

• File organization:

Which allows restructuring the data from one type to another?

1.3 Difference between File system & DBMS

File System

1. File system is a collection of data. Any management with the file system, user has to write the procedures

2. File system gives the details of the data representation and Storage of data.

3. In File system storing and retrieving of data cannot be done efficiently.

4. Concurrent access to the data in the file system has many problems like

a. Reading the file while other deleting some information, updating some information

5. File system doesn’t provide crash recovery mechanism.

Eg. While we are entering some data into the file if System crashes then content of the file is lost.

6. Protecting a file under file system is very difficult.

DBMS

1. DBMS is a collection of data and user is not required to write the procedures for managing the database.

2. DBMS provides an abstract view of data that hides the details.

3. DBMS is efficient to use since there are wide varieties of sophisticated techniques to store and retrieve the data.

4. DBMS takes care of Concurrent access using some form of locking.

5. DBMS has crash recovery mechanism, DBMS protects user from the effects of system failures.

6. DBMS has a good protection mechanism.

DBMS = Database Management System

RDBMS = Relational Database Management System

A database management system is, well, a system used to manage databases. A relational database management system is a database management system used to manage relational databases. A relational database is one where tables of data can have relationships based on primary and foreign keys.

1.4 Advantages of DBMS.

Due to its centralized nature, the database system can overcome the disadvantages of the file system-based system

1. Data independency:

Application program should not be exposed to details of data representation and storage DBMS provides the abstract view that hides these details.

2. Efficient data access.:

DBMS utilizes a variety of sophisticated techniques to store and retrieve data efficiently.

3. Data integrity and security:

Data is accessed through DBMS, it can enforce integrity constraints. E.g.: Inserting salary information for an employee.

4. Data Administration:

When users share data, centralizing the data is an important task, Experience professionals can minimize data redundancy and perform fine tuning which reduces retrieval time.

5. Concurrent access and Crash recovery:

DBMS schedules concurrent access to the data. DBMS protects user from the effects of system failure.

6. Reduced application development time.

DBMS supports important functions that are common to many applications.

1.5 Functions of DBMS

• Data Definition: The DBMS provides functions to define the structure of the data in the application. These include defining and modifying the record structure, the type and size of fields and the various constraints to be satisfied by the data in each field.

• Data Manipulation: Once the data structure is defined, data needs to be inserted, modified or deleted. These functions which perform these operations are part of DBMS. These functions can handle plashud and unplashud data manipulation needs. Plashud queries are those which form part of the application. Unplashud queries are ad-hoc queries which performed on a need basis.

• Data Security & Integrity: The DBMS contains modules which handle the security and integrity of data in the application.

• Data Recovery and Concurrency: Recovery of the data after system failure and concurrent access of records by multiple users is also handled by DBMS.

• Data Dictionary Maintenance: Maintaining the data dictionary which contains the data definition of the application is also one of the functions of DBMS.

• Performance: Optimizing the performance of the queries is one of the important functions of DBMS.

1.6 Role of Database Administrator.

Typically there are three types of users for a DBMS:

1. The END User who uses the application. Ultimately he is the one who actually puts the data into the system into use in business. This user need not know anything about the organization of data in the physical level.

2. The Application Programmer who develops the application programs. He/She has more knowledge about the data and its structure. He/she can manipulate the data using his/her programs. He/she also need not have access and knowledge of the complete data in the system.

3. The Data base Administrator (DBA) who is like the super-user of the system.

The role of DBA is very important and is defined by the following functions.

• Defining the schema: The DBA defines the schema which contains the structure of the data in the application. The DBA determines what data needs to be present in the system and how this data has to be presented and organized.

• Liaising with users: The DBA needs to interact continuously with the users to understand the data in the system and its use.

• Defining Security & Integrity checks: The DBA finds about the access restrictions to be defined and defines security checks accordingly. Data Integrity checks are defined by the DBA.

• Defining Backup/Recovery Procedures: The DBA also defines procedures for backup and recovery. Defining backup procedure includes specifying what data is to be backed up, the periodicity of taking backups and also the medium and storage place to backup data.

• Monitoring performance: The DBA has to continuously monitor the performance of the queries and take the measures to optimize all the queries in the application.

1.6 Simplified Database System Environment

A database management system (DBMS) is a collection of programs that enables users to create and maintain database. The DBMS is a general purpose software system that facilitates the process of defining, constructing, manipulating and sharing databases among various users and applications. Defining a database specifying the database involves specifying the data types, constraints and structures of the data to be stored in the database. The descriptive information is also stored in the database in the form database catalog or dictionary; it is called meta-data.

Manipulating the data includes the querrying the database to retrieve the specific data.

An application program accesses the database by sending the qurries or requests for data to DBMS.

The important function provided by the DBMS includes protecting the database and maintain the database.