Database management systems cs403 power point slides lecture 04
- 1. © Virtual University of Pakistan Database Management Systems Lecture - 4
- 2. © Virtual University of Pakistan Today’s Review Continue 3-L architecture Data Independence Different aspect of DBMS
- 3. © Virtual University of Pakistan Level 3 Internal or Physical View Concerns about the physical implementation of the database
- 4. © Virtual University of Pakistan Internal View DBMS chooses type of data structures lays out data on storage devices with operating system access methods
- 5. © Virtual University of Pakistan Internal View Internal record: a single stored record Does not just contain what we see at the conceptual level DBMS adds other data
- 6. © Virtual University of Pakistan Physical Level Generally same as Internal Actual representation of data on the storage device In the binary format OS responsibility
- 7. © Virtual University of Pakistan Inter-Schema Mappings Also a part of 3-level architecture External/conceptual mapping Conceptual/Internal
- 8. © Virtual University of Pakistan Ext/Con Mapping Specifies mapping between objects in the external view to those in the logical model
- 9. © Virtual University of Pakistan Con/Int Mapping Specifies mapping between objects in the logical model to those in the physical model- data independence
- 10. © Virtual University of Pakistan 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. © Virtual University of Pakistan 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. © Virtual University of Pakistan Data Independence
- 13. © Virtual University of Pakistan Data Independence A major outcome of 3-L Arch The immunity of applications to change in storage structure and access strategy
- 14. © Virtual University of Pakistan Changes in lower level do not affect the upper levels Don’t take it word to word Mind the direction please Data Independence
- 15. © Virtual University of Pakistan Data Independence Types • Logical Data Independence • Physical Data Independence
- 16. © Virtual University of Pakistan Logical Data Independence Changes in conceptual model do not affect the external views Immunity of external level from changes at conceptual level
- 17. © Virtual University of Pakistan Types of Changes Adding a new file/index etc. Adding a new field in a file Changing type/size Deleting an attribute
- 18. © Virtual University of Pakistan Physical Data Independence Changes in the internal model do not affect the conceptual model Immunity of Conceptual level from changes at Internal level
- 19. © Virtual University of Pakistan Changes Examples Changing file organization Index implementation, hash, tree etc. Changing storage medium
- 20. © Virtual University of Pakistan 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
- 21. © Virtual University of Pakistan Functions of DBMS Data Processing A User Accessible Catalog Transaction Support Concurrency Control Services
- 22. © Virtual University of Pakistan Functions of DBMS Recovery Services Authorization Services Support for Data Communication Integrity Services
- 23. © Virtual University of Pakistan DBMS Environments Single User Multi-user Teleprocessing File Servers Client-Server
- 24. © Virtual University of Pakistan Teleprocessing All processing at a central computer Dumb Terminals
- 25. © Virtual University of Pakistan File Servers LAN File returned Data request Database Workstation Workstation File Server
- 26. © Virtual University of Pakistan Client-Server LAN Selected data returned Data request Database Client Client Server (with DBMS)
- 27. © Virtual University of Pakistan Today’s Summary Completed 3-L architecture Discussed data independence Discussion on DBMS
- 28. © Virtual University of Pakistan Thanks and Allah Hafiz
- 29. © Virtual University of Pakistan Database Management Systems Lecture - 4