![Sequence [Todays Agenda]
Content of Lecture
•Continue 3-L architecture
•Data Independence
•Different Environments of DBMS](https://image.slidesharecdn.com/lec4database-250326042135-861764b5/85/Lecture-4-Database-management-system-ppt-3-320.jpg)
Lecture 4 Database management system.ppt
- 2. An overview of lecture - 3 • Database Architecture • Data Independence
- 3. Sequence [Todays Agenda] Content of Lecture •Continue 3-L architecture •Data Independence •Different Environments of DBMS
- 4. Level 3 Internal or Physical View • Concerns about the physical implementation of the database
- 5. Internal View • DBMS chooses type of data structures • lays out data on storage devices with operating system access methods
- 6. Internal View • Internal record: a single stored record • Does not just contain what we see at the conceptual level • DBMS adds other data
- 7. Inter-Schema Mappings • Also a part of 3-level architecture • External/conceptual mapping • Conceptual/Internal
- 8. Ext/Con Mapping • Specifies mapping between objects in the external view to those in the logical model
- 9. Con/Int Mapping • Specifies mapping between objects in the logical model to those in the physical model-data independence
- 10. 3-Level Architecture External Level Conceptual Level Internal Level Physical Data Organization Ext/Con Mapping View 1 View 2 View n Conceptual Schema Internal Schema Database User 1 User 2 User n Con/Int Mapping
- 11. Name DoB Deps DepId Rana Aslam 12/09/70 5 D001 Marya Wasti 29/02/80 0 D005 First Name: Rana Last Name: Aslam Date of Birth: 12 Sep, 1970 Name: R. Aslam Age: 24y,10d Dept: Sales Saleem Saleema 01110011010011100101001010100101010010101….. BH RH Rana Aslam 120970 5 D001 RH Marya Wasti…
- 12. Data Independence • A major outcome of 3-L Arch • The immunity of applications to change in storage structure and access strategy 12
- 13. Data Independence • Changes in the lower levels do not affect the upper levels • Don’t take it word to word • Mind the direction please 13
- 14. Data Independence Types • Logical Data Independence • Physical Data Independence 14
- 15. Logical Data Independence • Changes in the conceptual model do not affect the external model • Immunity of external level from changes at conceptual level 15
- 16. Type of Changes • Adding a new file • Adding a new field in a file • Changing type/ size • Deleting an attribute 16
- 17. Physical Data Independence • Changes in the internal model do not affect the conceptual model • Immunity of Conceptual level from changes at Internal level 17
- 18. Changes Examples • Changing file organization • Index implementation, hash, tree etc. • Changing storage medium 18
- 19. 3-Level Architecture External Level Conceptual Level Internal Level Physical Data Organization Ext/Con Mapping View 1 View n Conceptual Schema Internal Schema Database User 1 User n Con/Int Mapping Conceptual Data Ind Physical Data Ind
- 20. DBMS Environments • Single User • Multi-user • Teleprocessing • File Servers • Client-Server 20
- 21. Teleprocessing All processing at a central computer Dumb Terminals
- 22. File Servers LAN File returned Data request Database Workstation Workstation File Server
- 23. Client-Server LAN Selected data returned Data request Database Client Client Server (with DBMS)
- 24. Today’s Summary • Completed 3-L architecture • Discussed data independence • Discussion on DBMS 24
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