DATABASE M ANAGEMENT S YSTEMS Lecture 2

NEED OF DATABASE APPROACH  File Processing System was very Defective  Many Problems were Present  These Problems needed to be Solved  This was the Main Purpose of Adopting Database Approach 2 Muhammad Tehseen Qureshi

DATABASE APPROACH  In Database Approach Data of Single Organization is present in a Single File  For Example: In Relational Database Management Systems likeMicrosoft Access Data is Stored in a Single Database File. There are Present Different Tables in the Database File. Tables are Related to each other and in this way Data in one Table is Related to Data in another table  Database Approach Solves almost all the problems of File Processing System 3 Muhammad Tehseen Qureshi

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DATA REDUNDANCY  Data Redundancy means Data Replication  Occurs when Same Data is stored in Multiple Files Example: STUDENT DATA CONTROLLER EXAMINATION LIBRARY  In Database Environment Data is Shared among Different Users and Departments and the Data is mostly Present in a Centralized Location  This Solves Data Redundancy Problem 5 Muhammad Tehseen Qureshi

DATA INCOSISTENCY  Data Inconsistency Occurs from Data Redundancy  It Occurs when Data about a Single Thing is Different in Different Files  Was a Huge Problem in File Processing System  This Problem was Solved in Database Approach  This happened because Main Data is Present at a Single Point and all other Departments get data from that main Location STUDENT DATA CONTROLLER EXAMINATION LIBRARYSPORTS 6 Muhammad Tehseen Qureshi

DATA ISOLATION  Data Isolation Means Scattered Data  Was Another Main Problem in File Processing System because Each Department has Separate Set of Files and Data Retrieval from Multiple Files was Difficult to Implement Example: Suppose we have a Employee Data in One File and Income Tax Due Data in Another File. If we Want to Send Income Tax Information to all the Employees than Data has to be Retrieved from above two Files and moreover Data is not Related to each Other  Database Approach Solves this Problem because of Data Relationships with Each other EMPLOYEES Emp_ID EMP_Name EMP_Address EMP_Contact INCOME TAX Emp_ID Due_Tax 7 Muhammad Tehseen Qureshi

DATA INTEGRITY  Data Integrity Deals with the Correctness and Accuracy of Data  In File Processing System Data Integrity was not Possible because we could not define Set of Integrity Rules for Data Example:  Age Limit to Apply in MSC Class is 25 years  Roll Number cannot be Negative  These Integrity Rules are Very Easy to be Implemented in Database Approach  These Rules Ensure that Data is Correctly Entered 8 Muhammad Tehseen Qureshi

AUTOMICITY  Atomicity Deals with Transactions  A Transaction is a Collection of Steps that Define a Complete Process  Atomicity Defines that Either a Transaction occur Completely or it will not Occur Regardless it is near to Completion or Far From Completion Example:  We have two Bank Accounts Ac1 and Ac2  We want to Transfer Money from Ac2 to Ac1  This Involves following Sub Steps 1.Deduct Amount From Ac2 2.Add Amount to Ac1  Atomicity Defines that Either Both These Steps occur or none of them should Occur and Changes must be Rolled Back 9 Muhammad Tehseen Qureshi

PROGRAM DATA INDEPENDENCE  In File Processing Systems Applications were Developed According to the Format of Files used to Store Data  If the File Format has to be changed then Applications must also have to be changed Accordingly  Database Approach Solves this Problem because Data and Applications are Independent of each other  If the Database Format is changed than there is not much need to change Applications 10 Muhammad Tehseen Qureshi

DATA SECURITY  Data Security was an Important Issue in the File Processing System  Anyone having Access to the Data Files can Open, See and Change the Data in the Files  Security was a Big Issue  In Database Approach Security is Managed by using Passwords  There is no way to open database File without a Password 11 Muhammad Tehseen Qureshi

ACCESS LEVELS  Data Security was an Important Issue in the File Processing System  Anyone having Access to the Data Files can Open, See and Change the Data in the Files  There was no Access Level in the File Processing System  We couldn`t define Access Rights  In Database Access Levels can be defined  Different users can be given Different types of Rights  These Access Levels are Managed by DBA Example:  Data Entry Staff only has Access to Enter Data  Reporting Staff can only See the Data but cannot Change it  Administrators can Enter, View and Change Data  Chairman has rights to Everything 12 Muhammad Tehseen Qureshi

DATA SHARING  In File Processing System Data of Each Department is Separate and each Department has its own set of Applications  Only the Concerned Department have Access to Data  No other Department can Access or Share this Data  In Database Approach Data is Present in a Single Location and can be Shared by different Users or Departments STUDENT DATA CONTROLLER EXAMINATION LIBRARYSPORTS 13 Muhammad Tehseen Qureshi

DATA COMPACTNESS  Data Compactness means to Store Data in Compact Manner  Compact Manner means that Data takes Less Space on Disk  In File Processing Approach Data was Stored in Separate Files and hence Took Large Space and was Wastage of Storage Recourse  In Database Approach Data is Stored in Compact Manner and Mostly at a Central Location and thus it takes Less Amount of Space 14 Muhammad Tehseen Qureshi

EASIER REPORTING  Reporting is one of the Most Important Feature of Database Approach  We can Generate Various types of Reports from Data Stored in Database  Reports are Generated using SQL  Reporting Process was very Difficult in File Processing System because of the fact that Data was Scattered and Isolated 15 Muhammad Tehseen Qureshi

BACKUP AND RESTORE  Backup and Restore is very useful  These Facilities are needed in case of any problems of Hardware or Software Failure  These Facilities ensure that data is available whether a problem occurs or not  Data is very important  Data must be kept safe  Data Backup and Restore ensures the Safeness of Data  Using Database Approach we can take Regular Backups of Data on Monthly, Daily even Hourly basis  If any problem occurs then Data is available from Backup Source  We can Restore it from there 16 Muhammad Tehseen Qureshi

LESS DEVELOPMENT TIME  Database Management Systems also Provides us facility to Develop a Complete Database Application in Less Time  It provides us Facility to Generate Forms, Reports easily and hence it takes Less Time to develop Database Application  While in File Processing System first we have to design the File Format and then Design Application Program Strictly According to File Format 17 Muhammad Tehseen Qureshi

EASIER MAINTENANCE  Maintenance Means Some Changes  In File Processing System Data and Applications are Dependent  Change in One Requires Change in the other as well  Maintenance becomes Lengthy and Time Consuming  In Database Approach Program and Data are Independent  Change in One doesn`t Demand change in other  Maintenance is easy 18 Muhammad Tehseen Qureshi