1. Database system concept and Architecture

2. Data Models, Schemas, and Instance
Categories of Data Models
Schemas, Instance, and Database State
Three-schema Architecture and Data Independence
The three levels of the Architecture
Data Independence
Database languages and Interface
DBMS Language
DBMS Interfaces
The Database System Environment
DBMS component Modules
Database system Utilities
Centralize and Client/Server Architectures for DBMSs
Basic Client/Server
Two-tier Client/Server Architecture for DBMSs
Three-tier Client/Server Architectures for Web Applications
Classification of Database Management Systems
Summary

3. Data Models, Schemas, and Instance
Data Model: a collection of concepts that can be use to describes the structure of a database – provides the necessary means to achieve this abstractions.
Structure of Database mean the data types, relationships, and constraints that should hold for the data.

4. Categories of Data Models
Categorize by the type of concepts they use to describe the database structure
High level or Conceptual Data Model
Low-level or Physical Data Model
Representational or Implementation Data Model

5. Low Level Data Model
provide concepts that describe the details of how data is stored in the computer. Usually provided for specialists, not for typical end users.

6. High Level or Conceptual Data Model
provide concepts that are closed to the way many users perceive data.
Example: use concepts such as entities, attributes, and relationships among two or more entities.
Faculty
Fcode
F_name
Department
Dcode
D_name
Compose of 1 N
Student
D_code in

7. Representation or Implementation Data Models
provide concepts that may be understood by end users but they are not too far removed from the way data is organized with in the computer. This hide some details of data storage but can be implemented on a computer system in a direct way.
Faculty
Department
Fcode
F_name
Fcode
Dcode
D_name
Student
Fcode
Dcode
S_Add
S_name
SID

8. Schemas, Instances, and Database State
Database Schema
is the description of a data base
specified during database design
and is not expect to change frequency
Schema Diagram
A displayed schema example the diagram displays the structure of each record type but not the instance records.
It displays only some aspect schema, for example name of record types and data items and some type of constraints
Database state or snapshot
is the data in the database at a particular moment in time.
Also called the current set of occurrences or instances in the database

9. Distinction between database schema and database state
When define a new database => specify only database schema to DBMS
At this point “database state is empty state” no data.
Get initial state => loaded with initial data
At any point in time, the database has a current state (current snapshot)
DBMS stores the descriptions of the schema constructs and constraints (called meta-data) in DBMS Catalog

10. The three levels of the Architecture
……..
External level
(Individual user
Views)
Conceptual level
(community user
View)
Internal level
(Storage View)
The ANSI/SPARE architecture is divided into 3 levels
Internal Level
External Level
Conceptual Level

11. External View External level is individual user lever.
Each user has a language
For application programmer, the language will be either
conventional programming language (e.g. Java, C++)
Fourth-generation language
For the end user, the language will be either
a query language (SQL)
Special purpose language perhaps forms, or menu driven, tailored to that user’s requirements and supported by some application

12. Conceptual Level
Conceptual view is a representation of the entire information content of the database.
The conceptual view consists of many types of conceptual record.
The conceptual view is defined by means of the conceptual schema, which includes definitions of each of the various conceptual record types.
The conceptual schema is written using another data definition language, the conceptual DDL.
The conceptual DDL definitions must not involve any considerations of physical representation or access techniques at all.
They must be no reference in the conceptual schema to stored field representation, stored record sequence, indexes, hashing schemas, pointer, or any storage and access details.

13. Internal Level
Internal View is a low-level representation of the entire database; it consist of many occurrences of many types of internal record.
Internal record is the ANSI/SPARE term for the construct that we have been calling a stored record.
The internal view is described by means of the internal schema, which not only defines the various stored record types but also specifics what indexes exist, how stored fields are represented, what physical sequence the stored record are in, and so on.
The internal schema is written using yet another data definition language – the internal DDL.

14. Example External 1 DCL 1 EMPP, 01 EMPC.
2 EMP# CHAR(6) EMPNO PIC X(6).
2 SAL FIXED BN(31); DEPTNO PIC X(4).
External 1
Employee
Employee_number Char(6)
Department_Number Char(4)
Salary Decimal(5)
Conceptual
Stored_Emp Bytes=20
PREFIX BYTES=6,OFFSET=0
EMP# BYTES=6,OFFSET=6, INDEX=EMPX
DEPT# BYTES=4,OFFSET=12,
PAY# BYTES=4,ALIGN=FULLWORD,OFFSET=16
Internal
จากตัวอย่างที่แสดงในภาพนั้นจะพบว่า
ในระดับหลักการฐานข้อมูลประกอบด้วยข้อมูลของเอนติตีพนักงาน (Employee) โดยที่ข้อมูลของพนักงานแต่ละคนประกอบด้วย รหัสประจำตัวพนักงาน (Employee_number) ซึ่งเป็นตัวอักษร 6 หลัก รหัสแผนก (Department_number) เก็บในรูปตัวอักษรขนาด 4 หลัก และเงินเดือน (Salary) ซึ่งจัดเก็บบันทึกโดยมีชนิดของข้อมูลเป็นตัวเลขขนาด 5 หลัก
ในระดับภายในแสดงของข้อมูลที่เก็บบันทึกในสื่อที่เก็บบันทึกจริง ในรูปของ stored record ชื่อ Stored_emp มีความยาวในการจัดเก็บทั้งสิ้น 20 ไบต์ โดยใช้ 6 ไบต์สำหรับ prefix ซึ่งเก็บรายละเอียดเกี่ยวกับ Control Information และมี Stored_emp มีการสร้างดัชนีเรียงตาม EMP# โดยเก็บในแฟ้มดัชนีชื่อ empx ซึ่งรายละเอียดในส่วนนี้ผู้ใช้ไม่เป็นต้องทราบ
ระดับภายนอกเป็นส่วนของผู้ใช้แต่ละกลุ่มมองเห็นข้อมูล ซึ่งจะแตกต่างกันไปขึ้นกับสิทธิในการมองเห็นและลักษณะการใช้งานแตกต่างกันไปด้วย เช่นกรณีตัวอย่างผู้ใช้ภาษา C ทำการประมวลผลกับข้อมูลในฐานข้อมูลโดยใช้ภาษา C สิ่งที่ผู้ใช้สนใจคือระเบียน emp ที่แสดงในรูปของภาษา C ประกอบด้วย 2 ฟิลด์ คือ empno และ salary ผู้ใช้ COBOL ซึ่งทำการประมวลผลโดยใช้ภาษา COBOL สิ่งที่ผู้ใช้สนใจคือระเบียน EMPC ซึ่งประกอบด้วย 2 ฟิลด์คือ empno และ deptno

15. Stored Database (Internal View)
User A1
User A2
User B1
User B2
User B3
Host
Language
+DSL
Host
Language
+DSL
Host
Language
+DSL
Host
Language
+DSL
Host
Language
+DSL
External View A
*External
Schema B
External View B
*External
Schema A
External/conceptual
Mapping A
Conceptual/Internal
Mapping B
Schemas
And
mappings
built and
maintained by
the database
administrator
(DBA)
Database
Management
System
(DBMS)
Conceptual View
Conceptual/Internal
mapping
Storage
Structure
Definition
(internal
Schema)
Stored Database (Internal View)
*User interface

16. Mappings Conceptual/Internal mappings
defines the correspondence between the conceptual view and the stored database;
It specified how conceptual records and fields are represented at the internal level.
If the stored database is changes
If the change has effect to the stored database definition – then the conceptual/Internal mapping must be changes accordingly
The effects of changes must be isolated below the conceptual level, in order to preserve physical data independence.

17. External/Conceptual mapping
Defines the correspondence between a particular external view and the conceptual view.
Example field and record name change

18. Data Independence
Defines as the capacity to change the schema at one level of a database system without having to change the schema at the next higher level.
Define 2 types of data independence.
Logical Data independence
Physical Data independence

19. Logical Data independence
Logical Data independence is the capacity to change the conceptual schema without have to change external schemas or application program.
Example
Expand the database by adding record type or data item.
To change the constraints
To reduce the database by removing a record type
The external schemas that refer only to the database should not be affected.

20. Example Fcode F_name Dcode D_name S_Add S_name SID Tcode Fcode Dcode
Faculty
S_Add
S_name
SID
Student
Department
Tcode
Fcode
Dcode
S_Add
T_name
Teacher

21. Example 2 Teach Fcode F_name Dcode D_name S_Add S_name SID Tcode
Faculty
S_Add
S_name
SID
Student
Department
Tcode
T_name
Teach
Teacher
Create view teacher1
as select sid ,sname, T_name
from student, teach
where student.tcode = teach.tcode
Create view teacher1
as select sid ,sname, T_name
from student, teacher
where student.tcode = teacher.tcode
Select sid, sname, T_name
from teacher1

22. Physical Data independence
Physical Data independence is the capacity to change the conceptual schema, the external schemas need not be changed.
Change may be needed because some physical files had to be reorganized
Example
Creating additional access structures to improve the performance of retrieval or update

23. Database language and interface
DBMS language
Data definition language (DDL) is used by DBA and database designer to define schemas.
Storage Definition Language (SDL) is used to specify internal schema
Data Manipulation Language (DML) is a set of operation for retrieval insertion deletion and modifies the data.

24. DBMS Interfaces Menu Based Interfaces for web Clients or Browsing.
Form Based Interfaces
Graphical User Interfaces
Natural Languages Interfaces
Interface of Parametric Users
Interfaces for the DBA

25. The Database System Environment
DBMS Component Modules

26. Component modules of a DBMS and their interactions
Application Programmers
DBA staff
APPLICATION
PROGRAMS
Casual
users
Parametric
users
DDL
STATEMENTS
PRIVILEGED
COMMANDS
Precompiled
INTERACTIVE
Query
Host Language
Compiler
DML
STATEMENTS
Query
Complier
COMPILES
Transaction
System
Catalog/
Data
Dictionary A E
DDL
Complier B
DML
Complier C
Run-time
Database
Processor
execution
execution
create table student
(fCode varchar2(2),
fname varchar2(30)
primary key fcode);
Stored Data Manager D
Concurrency control/
Backup/Recovery subsystem
Stored Database

27. Data Dictionary The DBMS must provide a data dictionary function.
The data dictionary is a system database (not user database)
It contains “data about the data” called “meta-data or descriptor” – that is, definitions of those objects in the system, instead of just “raw data”.
It will keep all of various schemas and mapping and all of the various security and integrity constraints, both source and object form.
Other terms are “dictionary”, “catalog”, “data repository”.

28. Database System Utilities
Database Utility helps the DBA in managing the Database system
Loading : to create the initial version of the database from regular data file
Backup/Restore
File reorganization
Performance Monitoring

29. Tool and Application Environments, and Communications Facilities
Case tool
Application Development environment
Provide an environment for developing database applications including database design, GUI development, querying and updating and application program development.
Power Builder (Sybase)
JBuilder (Borland)
Communication software
Function allow users at location to remote from the database system site to access the database through the computer terminals, workstation, local computer.
Case – Computer aided software engineering, used in primary for database design

30. Centralized and Client/Server Architecture for DBMSs
Centralized DBMSs Architecture
Centralized DBMS => all DBMS function
All processing was performed remotely on the computer system, only display information and controls were sent from the computer to display terminal

31. Basic Client/Server
Idea is to define specialized servers with specific functionalities.
Client machines provide the user with the appropriate interfaces to utilize the server, and local processing power to run local application.
Client is a user machine that provide user interface capabilities and local processing. When requires process not in that machine it connects to a server that provide the needed functions.
Server is a machine that can provide service to the client machine.

32. Two main type of basic DBMS architectures on client/server frame work
Two-tier Client/Server Architecture
Three-tier Client/Server Architecture

33. Two-tier Client/Server
site1
Site2
Server
Site3
Site n ……
Communication Network
Program establishes a connection to the DBMS
ODBC : Open Database Connectivity (ODBC) provides an Application Programming Interface (API), which allows client-side program to call the DBMS

34. Three-tier Client/Server Architecture
Client contain GUI interface and some additional business rule
GUI
Web Interface
Application
Program
Web Pages
Database
Management
System
Client
Application Server Or
Web server
Server
This server plays an intermediate role by storing business rule (procedure/constraints) that are used to access data from the database server. Also improve database security.

35. Classification of DBMS
By Data Model
Relational Data Model
Object Data Model
Hierarchical and Network Data Models
By numbers of users supported by the system
Single User system
Multi User system
Number of Sites
Centralized => the data stored at a single computer site
Distributed DBMS (DDBMS) => have the actual database and DBMS software distributed over many sites
Homogenous DDBMSs
Heterogeneous DBMSs
Purpose
General Purpose
Special Purpose

36. Summary Introduces the main concepts used in database systems
Define Data model & distinguished three main categories of data models:
High-level/Conceptual
Low Level
Representation/Implementation
Schema -> description of a database
Describe the three-schema DBMS architecture
Internal, Conceptual and External
Main types of languages and interfaces that DBMSs support
DDL - define Database conceptual schema
DSL – specifying views and storage structures
DML – retrieval, update
Classified DBMS

37. Figure illustrates a typical variation of Oracle's memory and process structures

38. Memory Structures and Processes
The mechanisms of ORACLE execute by using memory structures and processes. All memory structures exist in the main memory of the computers that constitute the database system. Processes are jobs or tasks that work in the memory of these computers.
Memory Structures
ORACLE creates and uses memory structures to complete several jobs. For example, memory is used to store program code being executed and data that is shared among users. Several basic memory structures are associated with ORACLE: the system global area (which includes the database and redo log buffers, and the shared pool) and the program global area.
System Global Area (SGA) is a shared memory region allocated by ORACLE that contains data and control information for one ORACLE instance.
An ORACLE instance contains the SGA and the background processes.
The SGA is allocated when an instance starts and deallocated when the instance shuts down. Each instance that is started has its own SGA.
The Program Global Area (PGA) is a memory buffer that contains data and control information for a server process. A PGA is created by ORACLE when a server process is started. The information in a PGA depends on the configuration of ORACLE.

39. The relational model has three major aspects: Structures
Database Structures
The relational model has three major aspects:
Structures
Structures are well-defined objects that store the data of a database. Structures and the data contained within them can be manipulated by operations.
Operations
Operations are clearly defined actions that allow users to manipulate the data and structures of a database. The operations on a database must adhere to a pre-defined set of integrity rules.
Integrity Rule
Integrity rules are the laws that govern which operations are allowed on the data and structures of a database. Integrity rules protect the data and the structures of a database.

40. An ORACLE database has both a physical and a logical structure
An ORACLE database has both a physical and a logical structure. By separating physical and logical database structure, the physical storage of data can be managed without affecting the access to logical storage structures.
Logical Database Structure
An ORACLE database's logical structure is determined by: one or more tablespaces.
the database's schema objects (e.g., tables, views, indexes, clusters, sequences, stored procedures).
The logical storage structures, including tablespaces, segments, and extents, dictate how the physical space of a database is used. The schema objects and the relationships among them form the relational design of a database.

41. databases and tablespaces
Tablespaces and Data Files Tablespaces are the primary logical storage structures of any ORACLE database. The usable data of an ORACLE database is logically stored in the tablespaces and physically stored in the data files associated with the corresponding tablespace. Figure 2 illustrates this relationship.
Although databases, tablespaces, data files, and segments are closely related, they have important differences:
databases and tablespaces
An ORACLE database is comprised of one or more logical storage units called tablespaces. The database's data is collectively stored in the database's tablespaces.
tablespaces and data files
Each tablespace in an ORACLE database is comprised of one or more operating system files called data files. A tablespace's data files physically store the associated database data on disk.
databases and data files
A database's data is collectively stored in the data files that constitute each tablespace of the database. For example, the simplest ORACLE database would have one tablespace, with one data file. A more complicated database might have three tablespaces, each comprised of two data files (for a total of six data files).
schema objects, segments, and tablespaces
When a schema object such as a table or index is created, its segment is created within a designated tablespace in the database. For example, suppose a table is created in a specific tablespace using the CREATE TABLE command with the TABLESPACE option. The space for this table's data segment is allocated in one or more of the data files that constitute the specified tablespace. An object's segment allocates space in only one tablespace of a database.