Chapter 2 Database Environment 1 © Pearson Education Limited 1995, 2005 Prodi Ilmu Komputer, UAD, 2007 Prepared by Tawar A. Gunawan, M.Kom.

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1 Chapter 2 Database Environment 1 © Pearson Education Limited 1995, 2005 Prodi Ilmu Komputer, UAD, 2007 Prepared by Tawar A. Gunawan, M.Kom

2 Chapter 2 – Topik : Arsitektur Basis Data : Three Level Three Level : external, conceptual, and internal Bahasa Basis Data / SQL : DDL and DML. Model Data 2 © Pearson Education Limited 1995, 2005

3 Chapter 2 – Topik.. lanjutan Conceptual modeling. DBMS Software components of a DBMS. Arsitektur client–server. Transaction Processing Monitors. 3 © Pearson Education Limited 1995, 2005

4 Database Menyediakan abstract view / “penampakan” data bagi user Menyembunyikan mekanisme detail bagaimana data disimpan dan dimanipulasi User dengan level berbeda akan melihat data dengan cara berbeda DBMS saat ini menerapkan arsitektur ANSI- SPARC (The American National Standards Institute – Standards Planning and Reqiurements Committee) 4

5 Objectives of Three-Level Architecture Semua user harus mengakses data yang sama. Sebuah view tidak akan terpengaruh oleh perubahan pada view yang lain User tidak perlu mengetahui secara detail bagaimana data disimpan secara fisik 5 © Pearson Education Limited 1995, 2005

6 Objectives of Three-Level Architecture  DBA dapat mengubah struktur penyimpanan databases tanpa mempengaruhi user’s view.  Susunan database secara internal tidak boleh terpengaruh oleh perubahan pada media penyimpan.  DBA boleh mengubah struktur database tanpa mengubah/mengganggu kebutuhan user. 6 © Pearson Education Limited 1995, 2005

7 ANSI-SPARC Three-Level Architecture 7 © Pearson Education Limited 1995, 2005

8 Three-Level Architecture  Internal level : Menjelaskan bagaimana struktur penyimpanan data secara fisik dilakukan  Conceptual level : Menjelaskan data apa yang disimpan, serta bagaimana data-data itu saling berhubungan.  External Level: View pada level user, masing- masing user akan menerima informasi berbeda tergantung keperluan.  View1 : daftar karyawan denan gajinya,  View2 : daftar karyawan dengan kantor cabangnya. 8

9 ANSI-SPARC Three-Level Architecture  External Level  Users’ view of the database.  Describes that part of database that is relevant to a particular user.  Contoh : data detail mahasiswa dilihat oleh  Dosen Wali: data akademik detail per mahasiswa  Kaprodi: jumlah per angkatan  Dekan: jumlah per prodi  Ka BAA: jumlah peserta wisuda  Rektor: waktu tempuh masing-masing prodi 9 © Pearson Education Limited 1995, 2005

10 ANSI-SPARC Three-Level Architecture Conceptual Level ◦ Community view of the database. ◦ Describes what data is stored in database and relationships among the data. ◦ Meliputi :  Entitas, atrbut dan relationship  Constraints / aturan / batasan pada data  Informasi semantic / sintaks  Informasi security dan integrity 10 © Pearson Education Limited 1995, 2005

11 ANSI-SPARC Three-Level Architecture Internal Level ◦ Physical representation of the database on the computer. ◦ Describes how the data is stored in the database. ◦ Meliputi :  Alokasi space untuk data maupun indeks  Penempatan record  Kompresi data serta teknik enkripsi yang digunakan 11 © Pearson Education Limited 1995, 2005

12 Physical Level Dikelola oleh OS atas permintaan dari DBMS Sangat variatif tergantung DBMS dan OS Misal bagaimana mekanisme penyimpanan dilakukan jika pada sebuah tabel ditambahkan data baru Mata kuliah Sistem Berkas dan Sistem Operasi 12

13 Schema, Mapping dan Instance Database Schema : deskripsi database secara menyeluruh ◦External ◦Conceptual ◦Internal Mapping : pemetaan – konversi ◦External - Conceptual ◦Conceptual – Internal Instance : isi database, berubah setiap saat 13

14 Differences between Three Levels of ANSI- SPARC Architecture 14 © Pearson Education Limited 1995, 2005

15 Three Levels of ANSI-SPARC Architecture Disiapkan untuk menjaga data independence – ketidaktergantungan data, sehingga masing-masing level tidk saling mempengaruhi Data independence : ◦Logical Data Independence ◦Physical Data Independence 15

16 Data Independence Logical Data Independence ◦Antara External - Conceptual ◦ 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. 16 © Pearson Education Limited 1995, 2005

17 Data Independence Physical Data Independence ◦Antara Conceptual – Internal ◦ 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. 17 © Pearson Education Limited 1995, 2005

18 Data Independence and the ANSI-SPARC Three-Level Architecture 18 © Pearson Education Limited 1995, 2005

19 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. 19 © Pearson Education Limited 1995, 2005

20 Database Languages Data Manipulation Language (DML) ◦ Provides basic data manipulation operations on data held in the database. Procedural DML ◦ allows user to tell system exactly how to manipulate data. ◦ Menempel pada bahasa pemrograman ◦ Digunakan pada model data hirarkis dan network Non-Procedural DML = declarative language ◦ allows user to state what data is needed rather than how it is to be retrieved. ◦ Digunakan pada Relational DBMS ◦ SQL atau QBE Fourth Generation Languages (4GLs) 20 © Pearson Education Limited 1995, 2005

21 Data Model  Model Data Integrated collection of concepts for describing data, relationships between data, and constraints on the data in an organization. Konsep/Aturan/ bagaimana cara menyajikan data, termasuk hubungan antara data serta batasan- batasan mengenai data milik suatu organisasi  Komponen Data Model meliputi :  a structural part;  a manipulative part;  possibly a set of integrity rules. 21 © Pearson Education Limited 1995, 2005

22 Data Model Purpose ◦ To represent data in an understandable way. ◦ Menyajikan data denagan cara yg mudah dipahami Categories of data models include: ◦ Object-based ◦ Record-based ◦ Physical. 22 © Pearson Education Limited 1995, 2005

23 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 23 © Pearson Education Limited 1995, 2005

24 Relational Data Model 24 © Pearson Education Limited 1995, 2005

25 Network Data Model 25 © Pearson Education Limited 1995, 2005

26 Hierarchical Data Model 26 © Pearson Education Limited 1995, 2005

27 Conceptual Modeling --- pass  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 process of developing a model of information use that is independent of implementation details.  Result is a conceptual data model. 27 © Pearson Education Limited 1995, 2005

28 Functions of a DBMS  Data Storage, Retrieval, and Update.  A User-Accessible Catalog.  Transaction Support.  Concurrency Control Services.  Recovery Services. 28 © Pearson Education Limited 1995, 2005

29 Functions of a DBMS  Authorization Services.  Support for Data Communication.  Integrity Services.  Services to Promote Data Independence.  Utility Services. 29 © Pearson Education Limited 1995, 2005

30 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. 30 © Pearson Education Limited 1995, 2005

31 Components of a DBMS 31 © Pearson Education Limited 1995, 2005

32 Components of Database Manager (DM) 32 © Pearson Education Limited 1995, 2005

33 Multi-User DBMS Architectures Teleprocessing File-server Client-server 33 © Pearson Education Limited 1995, 2005

34 Teleprocessing  Traditional architecture.  Single mainframe with a number of terminals attached.  Trend is now towards downsizing. 34 © Pearson Education Limited 1995, 2005

35 File-Server  File-server is connected to several workstations across a network.  Database resides on file- server.  DBMS and applications run on each workstation. 35 © Pearson Education Limited 1995, 2005  Disadvantages include:  Significant network traffic.  Copy of DBMS on each workstation.  Concurrency, recovery and integrity control more complex.

36 Traditional Two-Tier Client-Server  Client (tier 1) manages user interface and runs applications.  Server (tier 2) holds database and DBMS. 36 © Pearson Education Limited 1995, 2005  Advantages include:  wider access to existing databases;  increased performance;  possible reduction in hardware costs;  reduction in communication costs;  increased consistency.

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38 Traditional Two-Tier Client-Server 38 © Pearson Education Limited 1995, 2005

39 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. 39 © Pearson Education Limited 1995, 2005

40 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. 40 © Pearson Education Limited 1995, 2005

41 Three-Tier Client-Server 41 © Pearson Education Limited 1995, 2005

42 Transaction Processing Monitors Program yang mengendalikan terjadinya transfer data antara client & server Untuk mengendalikan konsistensi lingkungan Banyak digunakan pada Online Transaction Processing (OLTP). 42 © Pearson Education Limited 1995, 2005

43 TPM as middle tier of 3-tier client-server 43 © Pearson Education Limited 1995, 2005