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Introduction An organization's survival relies on decisions made by management To make decisions, managers rely on good, timely, and relevant information. Information is obtained by === As data are the building blocks of information, quality of data is critical to quality of information, decision-making, and organizational well being. 1 Data and Information • • Data Raw Facts, without any meaning Managed by DBMS Information Has meaning, created by processing data. Combined with rules, produces knowledge Created and Reported by Management Information System. 2 Database a database is a structured collection of data and metadata that enable computer programs to find answers to queries Data retrieved in answer to these queries assume the form of information useful for decision making 3 Qualification for Database Most professionals consider collection of data as database only if it: is managed to ensure its integrity and quality allows shared access by a community of users has a schema supports a query language. 4 DBMS Complex set of software program that controls the organization, storage, management, and retrieval of data from a database Accepts requests for data from application program and instructs operating system to transfer the appropriate data Enables addition of new categories of data to the database without disruption to the existing system 5 Components of DBMS Modeling language to define schema of each database hosted according to the data model Data structures optimized to deal with huge data stored on a permanent data storage device Query language and report writer Transaction mechanism to ensure data integrity 6 Importance of DBMS Facilitates effective & efficient data management Facilitates information retrieval with ad hoc queries Facilitates access to large, organized data Promotes integrated view of an organization’s operations Reduces chance of data inconsistency 7 Functions of DBMS Manages data dictionary Manages data storage Responsible for data transformation & presentation Manages data integrity & security Controls multi-user access Manages backup & recovery Manages database language & API Manages database communication interface Manages video 8 Evolution Databases were first created to perform clerical tasks Later, they were designed for requesting information These needs were met through File Systems 9 File Systems File systems may be considered as less powerful database technology Data organized according to expected use Manual files systems were computerized by data Processing specialists 10 File System Terminology Field - Group of characters with specific meaning Record - Logically connected fields describing a person, place, or thing File - Collection of related records E.g. Telephone Directory 11 Problems with File System Extensive use of 3GL No support for ad hoc query Results in islands of Information Changing data characteristic requires modifying data access programs (data dependence) Changing file structure requires modifying related programs (structural dependence) 12 Problems with File System (Contd) No standard for field nomenclature Data Redundancy E.g. SSN, Socnum, Empid) Conflicting versions of same data Results of uncontrolled data redundancy Data anomalies Data inconsistency 13 Database Systems Logically related data stored in a single repository Elimination of inconsistency, data anomalies, data dependence, & structural dependence Storage of data structures, relationships, and access paths 14 Database vs. File Systems Figure 1.6 15 Database System Environment Figure 1.7 16 Types of Database Systems Single-user vs. multiple-user database Desktop, Workgroup, Enterprise Central vs. Distributed use Productional vs. Transactional Decision Support vs. Data Warehouse 17