1 / 8

DATABASE Management Systems

DATABASE Management Systems. Lecture 4. Three-Level Architecture. DBA should be able to change database storage structures without affecting the users’ views. Internal structure of database should be unaffected by changes to physical aspects of storage.

prem
Download Presentation

DATABASE Management Systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. DATABASE Management Systems Lecture 4

  2. Three-Level Architecture • DBA should be able to change database storage structures without affecting the users’ views. • Internal structure of database should be unaffected by changes to physical aspects of storage. • DBA should be able to change conceptual structure of database without affecting all users. Muhammad Tehseen Qureshi

  3. Three-Level Architecture Muhammad Tehseen Qureshi

  4. Three-Level Architecture • External Level • Users’ view of the database. • Describes that part of database that is relevant to a particular user. • Conceptual Level • Community view of the database. • Describes what data is stored in database and relationships among the data. Muhammad Tehseen Qureshi

  5. Three-Level Architecture • Internal Level • Physical representation of the database on the computer. • Describes how the data is stored in the database. Muhammad Tehseen Qureshi

  6. Data Independence • Logical Data Independence • Refers to immunity of external schemas to changes in conceptual schema. • Conceptual schema changes (e.g. addition/removal of entities). • Should not require changes to external schema or rewrites of application programs. Muhammad Tehseen Qureshi

  7. Data Independence • Physical Data Independence • Refers to immunity of conceptual schema to changes in the internal schema. • Internal schema changes (e.g. using different file organizations, storage structures/devices). • Should not require change to conceptual or external schemas. Muhammad Tehseen Qureshi

  8. Data Independence and the Three-Level Architecture Muhammad Tehseen Qureshi

More Related