Transcript ch1x

Introduction to
Databases
Dr. Osama AL Rababah
Objectives
In this capture you will learn:
• Some common uses of database systems.
• The characteristics of file-based.
• The problems with the file-based approach.
• The meaning of the term “database”.
• The meaning of the term “DBMS”.
• The typical functions of DBMS.
Objectives
• The major components of the DBMS environment.
• The personnel involved of the DBMS environment.
• The advantages and disadvantages of DBMSs.
introduction
• A database is a collection of information that is organized so
that it can easily be accessed, managed, and updated. In one
view, databases can be classified according to types of
content: bibliographic, full-text, numeric, and images.
• In computing, databases are sometimes classified according to
their organizational approach. The most prevalent approach is
the relational database, a tabular database in which data is
defined so that it can be reorganized and accessed in a
number of different ways. A distributed database is one that
can be dispersed or replicated among different points in a
network. An object-oriented programming database is one
that is congruent with the data defined in object classes and
subclasses.
common uses of database
systems
•
•
•
•
•
•
Purchases from the supermarket
Purchases using your credit card
Booking a vacation with a travel agent
Using the local library
Studying at a collage
And ….. More
The characteristics of file-based
• A flat file database describes any of various means to encode
a database model (most commonly a table) as a single file.
• A flat file can be a plain text file or a binary file. There are
usually no structural relationships between the records.
Problems with the file-based
•
•
•
•
Separation and isolation of data
Duplication of data (redundancy).
Program-Data dependence
Incompatible file format.
The meaning of “database”
• A database is a shared collection of logically related data and
its description, designed to meet the information needs of an
organization.
The meaning of “DBMS”
Database management systems (DBMSs) is a software system
that enables users to define, create, maintain, and control access
to the database.
The typical functions of DBMS.
•
•
•
•
•
•
•
•
•
Update and retrieve data
Provide catalog services
Support concurrent update
Recover data
Provide security services
Provide data integrity features
Support data independence
Support data replication
Provide utility services
1. Update and Retrieve Data
• Fundamental capability of a DBMS
• Users don't need to know how data is stored or
manipulated
• Users add, change, and delete records during
updates
• Users view and manipulate data during retrieval
2. Provide Catalog Services
•
•
•
•
•
Stores data about data
Contains descriptions of database components
Often hidden from users
Used by database administrators and programmers
Data dictionary in larger DBMSs
3. Support Concurrent Update
• Ensures accuracy when several users update
database at same time
• Manages complex scenarios for updates
4. Recovery
• Mechanism for recovering damaged database
• The return of database to correct state is called
recovery
• Simplest recovery involves using backups
• Other recovery methods
• Forward recovery
• Backward recovery
• PC-based
5. Provide Security Services
• Prevention of unauthorized access
• Encryption - converts data to indecipherable form
• Authentication - identification of DBMS user,
often with passwords or biometrics
• Authorizations - rules to specify data available
to certain users
• Views
• Privacy
6. Provide Data Integrity
Features
• Rules followed to ensure data is accurately and
consistently updated
• Key integrity
• Foreign key and primary key constraints
• Data integrity
• Data type
• Legal values
• Format
7. Support Data Independence
• Programs must be independent of database
structure
• Considerations
• Adding a field
• Changing length of field
• Creating an index
• Adding or changing a relationship
8. Support Data Replication
• Manage multiple copies of same data in multiple
locations
• Maintained for performance or other reasons
• Ease of access and portability
9. Provide Utility Services
•
•
•
•
•
Assist in general database maintenance
Permit changes to database structure
Permit addition and deletion of indexes
Provide access to operating system services
Support for queries, screen generators, and
report generators
(1)
9. Provide Utility Services
(2)
• Provide Utility Services (cont.)Provide support for embedded
procedures
• Procedural
• Nonprocedural
• Provide easy-to-use, menu-driven interface
components of the DBMS
environment.
1.
2.
3.
4.
5.
Hardware
Software
Data
Procedures
People
Roles in Database Environment
•
•
•
•
Data and Database Administrator. (DA) and(DBA)
Database Designer
Application Developer
End-Users
Advantages of DBMS
•
•
•
•
•
•
(1)
Control of data redundancy
Data consistency
More information from the same amount of data
Sharing of data
Improved data integrity
Improved security
Advantages of DBMS
•
•
•
•
•
•
•
•
(2)
Enforcement of standards
Economy of scale
Balance of conflicting requirements
Improved data accessibility and responsiveness
Increased productivity
Improved maintenance throw data independence
Increased concurrency
improved backup and recovery services
Disadvantages of DBMS
•
•
•
•
•
•
•
Complexity
Size
Cost of DBMSs
Additional hardware cost
Cost of conversion
Performance
Greater impact of failure
Think and answer
1. Describe the approach of file-based systems. And discuss the
disadvantages
2. Discuss the role of the following personnel
- DA
- DBA
- Application developer
- End-users