1. Chapter 2
Database
Archetecture
Welcome to chapter 2

2. 2017/4/23
Chapter 2
Archetecture 2

3. The content 1).Database Users 2).Benifits of Database
3).History of database
4).Data Model, Schema
5). Three-Schema Architecture
6). Database Architecture
Difficulty: Three-Schema Architecture
Focus on: Three-Schema Architecture
Hours:2 hours
Teaching way: ppt

4. Database Users Database Designers: End-users:
They are responsible to define the content, the structure, the constraints, and functions or transactions in the database. They must communicate with the end-users and understand their needs.
End-users:
They use the data for queries, reports and some of them actually update the database content.

5. Database Administrator
Coordinates all the activities of the database system
has a good understanding of the enterprise’s information resources and needs.
Database administrator's duties include:
Storage structure and access method definition
Define the structure of the database
Granting users authority to access the database
Backing up data
Monitoring performance and responding to changes

6. Database Administrator Duties
DBA Responsibilities
Install and upgrade ORACLE server and applications
Create primary database storage and primary objects
Allocate system storage and plan future storage needs
Modify the database structures
Enroll and monitor user access to the database
Back up and recover the database
Maintain system Security
Monitor and optimize performance
DATABASE
ADMINISTRATOR
Startup and Shut Down the database
Create
Primary
Storage
Structures
Backup
and
Recovery
Understand
the Oracle
Architecture
Enroll and
Monitor
Users
Grant and
Revoke
Privileges
Manage
Database
Design a
Database

7. Benefits of Database Technology
Timetable
Student
Admin
Scheduler
Payroll
Year List
Cheques
Students
Course Data
Lecturer Data
DataBase Management System
Database
- Controlling redundancy in data storage and in development and maintenance efforts.
- Sharing of data among multiple users.
- Restricting unauthorized access to data.
- Providing multiple interfaces to different classes of users.
- Representing complex relationships among data.
- Enforcing integrity constraints on the database.
- Providing backup and recovery services.
- Potential for enforcing standards.
- Flexibility to change data structures.
- Reduced application development time.
- Availability of up-to-date information.
Economies of scale.

8. History of Database Systems
1950s and early 1960s:
Data processing using magnetic tapes for storage
Tapes provide only sequential access
Punched cards for input
Late 1960s and 1970s:
Hard disks allow direct access to data
Network and hierarchical data models in widespread use
After 1970 :
Ted Codd defines the relational data model
High-performance (for the era) transaction processing

9. Hierarchical Database Model
Logically represented by an upside down tree
Each parent can have many children
Each child has only one parent

10. Network Database Model
Each record can have multiple parents
Composed of sets
Each set has owner record and member record
Member may have several owners
Student dorm
students
Teaching group
department
teachers
Storage structure: linked list, dual linked list

11. Relational Database Model
Storage structure: tables stored as files

12. History
1980s:
Research relational prototypes evolve into commercial systems
SQL becomes industry standard
Parallel and distributed database systems
Object-oriented database systems
1990s:
Large decision support and data-mining applications
Large multi-terabyte data warehouses
Emergence of Web commerce
2000s:
XML and XQuery standards
Automated database administration
Increasing use of highly parallel database systems
Web-scale distributed data storage systems

13. Extending Database Capabilities
New functionality is being added to DBMSs in the following areas:
Scientific Applications
Image Storage and Management
Audio and Video data management
Data Mining
Spatial data management
Time Series and Historical Data Management
The above gives rise to new research and development in incorporating new data types, complex data structures, new operations and storage and indexing schemes in database systems.

14. Data Models A collection of tools for describing
Data structure
Data operation
Data constraints
Categories of data models:
1.Conceptual (high-level, semantic) data models: Provide concepts that are close to the way many users perceive data. Conceptual data models use concepts such as entities, attributes, and relationships. Entity-Relationship data model (mainly for database design) m 讲授 组成 成绩 选修 课程 班级 学生 管理 n 1
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15. Categories of data models
Physical (low-level, internal) data models: Provide concepts that describe details of how data is stored in the computer by representing information such as record formats, record orderings, and access paths. An access path is a structure that makes the search for particular database records efficient.
Implementation (representational) data models: Provide concepts that fall between the above two, balancing user views with some computer storage details. The models used here are most frequently in traditional commercial DBMSs, and they include the widely-used relational data model, network and hierarchical ,Object-based data models (Object-oriented and Object-relational)
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Slide 2-15

16. Instances and Schemas (321,Jones,Owens)
Similar to types and variables in programming languages
Schema – the logical structure of the database
Example: The database consists of information about a set of customers and accounts and the relationship between them)
Analogous to type information of a variable in a program
Instance – the actual content of the database at a particular point in time
Analogous to the value of a variable
Student(studno,name,address)
Course(courseno,lecturer)
Student(123,Bloggs,Woolton)
(321,Jones,Owens)

17. Levels of Abstraction type customer = record
Physical level: describes how a record (e.g., customer) is stored.
Logical level: describes data stored in database, and the relationships among the data.
type customer = record
customer_id : string; customer_name : string; customer_street : string; customer_city : string;
end;
View level: application programs hide details of data types. Views can also hide information (such as an employee’s salary) for security purposes.

18. An architecture for a database system
View of Data
An architecture for a database system

19. Three-Schema Architecture
Mappings among schema levels are needed to transform requests and data. Programs refer to an external schema, and are mapped by the DBMS to the internal schema for execution.
Logical Data Independence: The capacity to change the conceptual schema without having to change the external schemas and their application programs.
Physical Data Independence: The capacity to change the internal schema without having to change the conceptual schema.
When a schema at a lower level is changed, only the mappings between this schema and higher-level schemas need to be changed in a DBMS that fully supports data independence. The higher-level schemas themselves are unchanged. Hence, the application programs need not be changed since they refer to the external schemas.
Slide 2-19

20. Database Management System Internals
Storage management
Query processing
Transaction processing

21. Storage Management
Storage manager is a program module that provides the interface between the low-level data stored in the database and the application programs and queries submitted to the system.
The storage manager is responsible to the following tasks:
Interaction with the file manager
Efficient storing, retrieving and updating of data
Issues:
Storage access
File organization
Indexing and hashing

22. Query Processing 1. Parsing and translation 2. Optimization
3. Evaluation

23. Transaction Management
A transaction is a collection of operations that performs a single logical function in a database application
Transaction-management component ensures that the database remains in a consistent (correct) state despite system failures (e.g., power failures and operating system crashes) and transaction failures.
Concurrency-control manager controls the interaction among the concurrent transactions, to ensure the consistency of the database.

24. Overall System Structure

25. DBMS Languages
High Level or Non-procedural Languages: e.g., SQL, are set-oriented and specify what data to retrieve than how to retrieve. Also called declarative languages.
Data Definition Language (DDL): Used by the DBA and database designers to specify the conceptual schema of a database.
Data Manipulation Language (DML): Used to specify database retrievals and updates.
Example: select age from student where name=‘Tom’
Slide 2-25

27. Database System Utilities
To perform certain functions such as:
- Loading data stored in files into a database.
- Backing up the database periodically on tape.
- Reorganizing database file structures.
- Report generation utilities.
- Performance monitoring utilities.
- Other functions, such as sorting , user monitoring , data compression , etc.
Data dictionary / repository:
- Used to store schema descriptions and other information such as design decisions, application program descriptions, user information, usage standards, etc.
- Active data dictionary is accessed by DBMS software and users/DBA.
- Passive data dictionary is accessed by users/DBA only.

30. DBMS Interfaces Stand-alone query language interfaces.
Programmer interfaces for embedding DML in programming languages:
Pre-compiler Approach
Procedure (Subroutine) Call Approach
User-friendly interfaces:
Menu-based, popular for browsing on the web
Forms-based, designed for naïve users
Graphics-based (Point and Click, Drag and Drop etc.)
Natural language: requests in written English
Combinations of the above
Slide 2-30

31. Other DBMS Interfaces Speech as Input (?) and Output
Web Browser as an interface
Parametric interfaces (e.g., bank tellers) using function keys.
Interfaces for the DBA:
Creating accounts, granting authorizations
Setting system parameters
Changing schemas or access path
Slide 2-31

32. Database Architecture
The architecture of a database systems is greatly influenced by
the underlying computer system on which the database is running:
Centralized
Client-server
Parallel (multiple processors and disks)
Distributed

33. A physical centralized architecture.

34. Logical two-tier client/server architecture.

35. Physical two-tier client-server architecture.

36. Logical three-tier client/server architecture.

37. Classification of DBMSs
Based on the data model used:
- Traditional: Relational, Network, Hierarchical.
Emerging: Object-oriented, Object-relational, Semi-structured
Other classifications:
- Single-user (typically used with micro- computers) vs. multi-user (most DBMSs).
Centralized (uses a single computer with one database) vs.
distributed (uses multiple computers, multiple databases)
Distributed Database Systems have now come to be known as client server based database systems because they do not support a totally distributed environment, but rather a set of database servers supporting a set of clients.

38. Summary From this lecture you can learn : 1).Database Users
2).Benifits of Database
3).History of database
4).Data Model, Schema
5). Three-Schema Architecture

39. Any Questions?
If there are any outstanding questions you can ask me one-to-one after the lecture OR privately in my office.

40. Exercises
1.what is three-schema architecture?