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Database Environment

Database Environment. Chapter 2. The Three-Level ANSI-SPARC Architecture. External Level Conceptual Level Internal Level Physical Data. External Level. The users view of the database. This level describes that part of the database that is relevant to the user. Conceptual Level.

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Database Environment

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  1. Database Environment Chapter 2

  2. The Three-Level ANSI-SPARCArchitecture • External Level • Conceptual Level • Internal Level • Physical Data

  3. External Level • The users view of the database. This level describes that part of the database that is relevant to the user

  4. Conceptual Level • The community view of the database. This level describes what data is stored in the database and the relationships among data. • This level represents • All entities and their attributes and their relationships • The constraints on the data • Semantic information about the data • Security and Integrity of Information

  5. Internal Level • This level describes the physical representation of the data on the computer. • Schemas, mapping and instances • Data Independence • Logical data independence ( Immunity of the external schema to changes in the conceptual schema) • Physical data independence ( Immunity of the conceptual schema to changes in the internal schema_

  6. Database Languages • The Data Definition Language • The Data Manipulation Language • Procedural DML • Nonprocedural DML • Fourth Generation Languages • Form Generators, Report Generators, Graphics Generators, Application Generators

  7. Data Models and Conceptual Modeling • Data Model – An Integration collection of concepts to describe and manipulate data • Object-Based Data Models • Entity-Relationship • Semantic • Record-Based Model • Relational • Network • Hierarchical

  8. Components of a DBMS • Query processor • Database Manager • File Manager • DML processor • DDL complier • Catalog Manager

  9. Software Components of the Database Manager • Authorization Control • Command Processor • Integrity Checker • Query Optimizer • Transaction Manager • Schedule • Recover Manager • Buffer Manager

  10. Multi-User DBMS Architecture • Teleprocessing • File-Server • Client-Server

  11. System Catalogs • A Repository of Information describing the data in the database

  12. Functions of a DBMS • Storage, Retrieval and Update • A User-accessible catalog • Transaction Support • Concurrency Control and Services • Authorization Services • Support for Data Communication • Integrity Services • Services to Promote Data Independence • Utility Services

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