1. CENG 352 Database Management Systems Nihan Kesim Çiçekli email: nihan@ceng.metu.edu.tr URL: http://www.ceng.metu.edu.tr/~nihan

2. CENG 352 Instructor: Nihan Kesim Çiçekli Office: A308 Email: nihan@ceng.metu.edu.tr Lecture Hours: Tue. 11:40 (BMB5); Thu. 10:40-12:30 (BMB5) Course Web page: http://cow.ceng.metu.edu.tr Teaching Assistant: Ömer Baykal, obaykal@ceng.metu.edu.tr 2

3. Required Background Material from CENG351 (Entity- Relationship modeling, relational data model, relational algebra, SQL, B+-trees and hash-based indexing, algorithms for sorting/merging data files) Intermediate programming skills –C/C++/Java 3

4. Text Books and References 1.Raghu Ramakrishnan, Database Management Systems, McGraw Hill, 3 rd edition, 2003 (text book). 2.R. Elmasri, S.B. Navathe, Fundamentals of Database Systems, 4 th edition, Addison-Wesley, 2004. 3.A. Silberschatz, H.F. Korth, S. Sudarshan, Database System Concepts, McGraw Hill, 4 th edition, 2002. 4.H. Garcia-Molina, J. D. Ullman, J. Widom, Database Systems The Complete Book, Prentice Hall, 2002. 4

5. Course Outline Review of the Relational Data Model Database Application Development Relational Database Design and Tuning Transaction Processing Concurrency Control Crash Recovery Query Processing Query Optimization 5

6. Grading Midterm 25 % Assignments and Quizzes 25 % Project 20 % Final Exam 30 % 6

7. Grading Policies Policy on missed midterm: –no make-up exam; compensated at final (only for the legal excuses and if informed beforehand) Policy on final exam: –Get at least 30% points from at least one of the written assignments and at least 30% points from the programming assignment –Attendance should be > 50% Lateness policy: –No late submission for the written assignments. –For the programming homework(s): can be late up to 7 days. Afterwards, will be penalized by 10%* day 2 –The last assignment may not be turned in late –All assignments are to be your own work. 7

8. Project Projects in groups. –Determine your groups till the end of add/drops. 3 stages: –Proposal Report (E/R) –Design Report –Final Report + Demo 8

9. Introduction 9

10. File-Based Systems Collection of application programs that perform services for the end users (e.g. reports). Each program defines and manages its own data. 10

11. File-Based Processing Pearson Education © 2009 11

12. Limitations of File-Based Approach Separation and isolation of data –Each program maintains its own set of data. –Users of one program may be unaware of potentially useful data held by other programs. Duplication of data –Same data is held by different programs. –Wasted space and potentially different values and/or different formats for the same item. 12

13. Limitations of File-Based Approach Data dependence –File structure is defined in the program code. Incompatible file formats –Programs are written in different languages, and so cannot easily access each other’s files. Fixed Queries/Proliferation of application programs –Programs are written to satisfy particular functions. –Any new requirement needs a new program. 13

14. Database Approach Arose because: –Definition of data was embedded in application programs, rather than being stored separately and independently. –No control over access and manipulation of data beyond that imposed by application programs. Result: –the database and Database Management System (DBMS). 14

15. Database Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization. System catalog (metadata) provides description of data to enable program–data independence. Logically related data comprises entities, attributes, and relationships of an organization’s information. 15

16. Database Management System (DBMS) A software system that enables users to define, create, maintain, and control access to the database. (Database) application program: a computer program that interacts with database by issuing an appropriate request (SQL statement) to the DBMS. 16

17. 17 Typical DBMS Functionality Define a database : in terms of data types, structures and constraints Construct or load the database on a secondary storage medium Manipulating the database : querying, generating reports, insertions, deletions and modifications to its content Concurrent Processing and Sharing by a set of users and programs – yet, keeping all data valid and consistent 17

18. Database Management System (DBMS) Pearson Education © 2009 18

19. Database Approach Data definition language (DDL). –Permits specification of data types, structures and any data constraints. –All specifications are stored in the database. Data manipulation language (DML). –General enquiry facility (query language) of the data. 19

20. Database Approach Controlled access to database may include: –a security system –an integrity system –a concurrency control system –a recovery control system –a user-accessible catalog. 20

21. Views Allows each user to have his or her own view of the database. A view is essentially some subset of the database. 21

22. Views - Benefits Reduce complexity Provide a level of security Provide a mechanism to customize the appearance of the database Present a consistent, unchanging picture of the structure of the database, even if the underlying database is changed 22

23. Disadvantages of DBMSs Complexity Size Cost of DBMS Additional hardware costs Performance Higher impact of a failure 23

24. Components of DBMS Environment Hardware –Can range from a PC to a network of computers. Software –DBMS, operating system, network software (if necessary) and also the application programs. Data –Used by the organization and a description of this data called the schema. Procedures –Instructions and rules that should be applied to the design and use of the database and DBMS. People 24

25. Roles in the Database Environment Data Administrator (DA) Database Administrator (DBA) Database Designers (Logical and Physical) Application Programmers End Users (naive and sophisticated) 25

26. History of Database Systems First-generation –Hierarchical and Network Second generation –Relational Third generation –Object-Relational –Object-Oriented 26

27. Data Model Integrated collection of concepts for describing data, relationships between data, and constraints on the data in an organization. –Purpose is to represent data in an understandable way. Data Model comprises: –a structural part; –a manipulative part; –possibly a set of integrity rules. 27

28. Data Models Object-Based Data Models –Entity-Relationship –Semantic –Functional –Object-Oriented. Record-Based Data Models –Relational Data Model –Network Data Model –Hierarchical Data Model. Physical Data Models Pearson Education © 2009 28

29. Relational Data Model Pearson Education © 2009 29

30. Network Data Model Pearson Education © 2009 30

31. Hierarchical Data Model Pearson Education © 2009 31

32. Conceptual Modeling Conceptual schema is the core of a system supporting all user views. Should be complete and accurate representation of an organization’s data requirements. Conceptual modeling is the process of developing a model of information use that is independent of implementation details. The result is the conceptual schema. 32

33. Objectives of 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. 33

34. Three-Level Architecture 34

35. 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. Internal Level –Physical representation of the database on the computer. –Describes how the data is stored in the database. 35

36. Differences between Three Levels of the Architecture Pearson Education © 2009 36

37. 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. 37

38. 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. 38

39. Data Independence and the Three- Level Architecture Pearson Education © 2009 39

40. Database Languages Data Definition Language (DDL) –Allows the DBA or user to describe and name entities, attributes, and relationships required for the application –plus any associated integrity and security constraints. Data Manipulation Language (DML) –Provides basic data manipulation operations on data held in the database. 40

41. System Catalog Repository of information (metadata) describing the data in the database. One of the fundamental components of DBMS. Typically stores: –names, types, and sizes of data items; –constraints on the data; –names of authorized users; –data items accessible by a user and the type of access; –usage statistics. 41

42. The DBMS Marketplace Relational DBMS companies – Oracle, Sybase – are among the largest software companies in the world. IBM offers its relational DB2 system. Microsoft offers SQL-Server, plus Microsoft Access for the cheap DBMS on the desktop, answered by “lite” systems from other competitors. Relational companies also challenged by “object-oriented DB” companies. But countered with “object-relational” systems, which retain the relational core while allowing type extension as in OO systems. 42

43. Three Aspects to Studying DBMS's 1. Modeling and design of databases. –Allows exploration of issues before committing to an implementation. 2. Programming: queries and DB operations like update. –SQL 3. DBMS implementation. 43

44. Components of a DBMS Major components of a DBMS: –Query processor –Database manager (DM) –File manager –DML preprocessor –DDL compiler –Catalog manager 44

45. Components of a DBMS Major software components for database manager –Authorization control –Command processor –Integrity checker –Query optimizer – Transaction manager – Scheduler – Recovery manager – Buffer manager 45

46. Components of a DBMS Pearson Education © 2009 46

47. Components of Database Manager (DM) Pearson Education © 2009 47

48. Multi-User DBMS Architectures Teleprocessing File-server Client-server 48

49. Teleprocessing Traditional architecture. Single mainframe with a number of terminals attached. Trend is now towards downsizing. Pearson Education © 2009 49

50. File-Server File-server is connected to several workstations across a network. Database resides on file-server. DBMS and applications run on each workstation. Disadvantages include: –Significant network traffic. –Copy of DBMS on each workstation. –Concurrency, recovery and integrity control more complex. Pearson Education © 2009 50

51. File-Server Architecture Pearson Education © 2009 51

52. Traditional Two-Tier Client-Server Client (tier 1) manages user interface and runs applications. Server (tier 2) holds database and DBMS. Advantages include: –wider access to existing databases; –increased performance; –possible reduction in hardware costs; –reduction in communication costs; –increased consistency. Pearson Education © 2009 52

53. Traditional Two-Tier Client-Server Pearson Education © 2009 53

54. Traditional Two-Tier Client-Server Pearson Education © 2009 54

55. Three-Tier Client-Server Client side presented two problems preventing true scalability: –‘Fat’ client, requiring considerable resources on client’s computer to run effectively. –Significant client side administration overhead. By 1995, three layers proposed, each potentially running on a different platform. 55

56. Three-Tier Client-Server Advantages: –‘Thin’ client, requiring less expensive hardware. –Application maintenance centralized. –Easier to modify or replace one tier without affecting others. –Separating business logic from database functions makes it easier to implement load balancing. –Maps quite naturally to Web environment. 56

57. Three-Tier Client-Server Pearson Education © 2009 57