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Note for Database Management System - DBMS By Amity Kumar

  • Database Management System - DBMS
  • Note
  • Amity University - AMITY
  • Computer Science Engineering
  • 18 Topics
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easily. • Data maintenance: Maintenance is the task concerned with keeping the data upto-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. Page 3

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1.1 • 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. Page 4

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• File organization: Which allows restructuring the data from one type to another? 1.2 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 Page 5

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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. 1.3 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. Page 6

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