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Note for Database Management System - DBMS By Thanmayee Tumuluri

  • Database Management System - DBMS
  • Note
  • DVR & Dr. HS MIC College of Technology - MIC
  • Computer Science Engineering
  • Uploaded 6 months ago
Thanmayee Tumuluri
Thanmayee Tumuluri
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UNIT -1 The Worlds of Database Systems INTRODUCTION TO BASIC CONCEPTS OF DATABASE SYSTEMS: What is Data? The raw facts are called as data. The word “raw” indicates that they have not been processed. Ex: For example 89 is the data. What is information? The processed data is known as information. Ex: Marks: 89; then it becomes information. What is Knowledge? 1. Knowledge refers to the practical use of information. 2. Knowledge necessarily involves a personal experience. DATA/INFORMATION PROCESSING: The process of converting the data (raw facts) into meaningful information is called as data/information processing. When Data When Information Processed Knowledge Processed Note: In business processing knowledge is more useful to make decisions for any organization. 5

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DIFFERENCE BETWEEN DATA AND INFORMATION: DATA 1.Raw facts 2. It is in unorganized form 3. Data doesn’t help decision making process INFORMATION 1.Processed data 2. It is in organized form in 3. Informationhelpsin decision making process FILE ORIENTED APPROACH: The earliest business computer systems were used to process business records and produce information. They were generally faster and more accurate than equivalent manual systems. These systems stored groups of records in separate files, and so they were called file processing systems. 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. The typical file-oriented system is supported by a conventional operating system. Permanent records are stored in various files and a number of different application programs are written to extract records from and add records to the appropriate files. 6

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DISADVANTAGES OF FILE-ORIENTED SYSTEM: The following are the disadvantages of File-Oriented System: Data Redundancy and Inconsistency: Since files and application programs are created by different programmers over a long period of time, the files are likely to be having different formats and the programs may be written in several programming languages. Moreover, the same piece of information may be duplicated in several places. This redundancy leads to higher storage and access cost. In addition, it may lead to data inconsistency. Difficulty in Accessing Data: The conventional file processing environments do not allow needed data to be retrieved in a convenient and efficient manner. Better data retrieval system must be developed for general use. Data Isolation: Since data is scattered in various files, and files may be in different formats, it is difficult to write new application programs to retrieve the appropriate data. Concurrent Access Anomalies: In order to improve the overall performance of the system and obtain a faster response time, many systems allow multiple users to update the data simultaneously. In such an environment, interaction of concurrent updates may result in inconsistent data. Security Problems: Not every user of the database system should be able to access all the data. For example, in banking system, payroll personnel need only that part of the database that has information about various bank employees. They do not need access to information about customer accounts. It is difficult to enforce such security constraints. Integrity Problems: The data values stored in the database must satisfy certain types of consistency constraints. For example, the balance of a bank account may never fall below a prescribed amount. These constraints are enforced in the system by adding appropriate code in the various 7

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