1. Characteristics of the Database Approach (Difference between traditional file processing and database approach)
Redundancy
Self-Describing nature of a database system: complete definition or description of the database structure and constraints are stored in the system catalog and the information stored in the catalog is called meta-data.
Insulation between Programs and Data, and Data Abstraction: (structure) program-data independence, program-operation independence, data abstraction: the characteristics that allow program-data independence, program-operation independence.
Multiple views of the data
Sharing of data and multiuser transaction processing : concurrency control (on-line transaction processing(OLTP) application)
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2. Advantages of Using a DBMS
Controlling Redundancy: duplication, wastage of storage space, inconsistent
Restricting Unauthorized Access
Providing Persistent Storage for Program Objects and Data Structures: object-oriented database. OODB are compatible with C++, Java.
Permitting Inferencing and Actions Using Deduction Rules: deduction database system (declarative language), active database system (event-condition-action)
Providing Multiple User Interfaces
Representing Complex Relationships Among Data
Enforcing Integrity Constraints: change in the code due to constraint enforced.
Providing Backup and Recovery
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3. Actors on the scene
Database Administrator (DBA): Administering database, DBMS and related software.
Database Designers: Identifying data, choosing appropriate structure to represent and store this data. Interacting with users.
End users
Casual end users
Naïve or parametric end users: Bank teller, Reservation Clerk.
Sophisticated end users: engineers, scientists, business analyst.
Stand alone users
System Analysts and Application Programmers (Software engineers): determine requirements of end users (specification), implement, test, debug and document
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4. Workers behind the scene
DBMS system designers and implementers: who design and implement the DBMS modules and interfaces as a software package.
Tool developers: develops software packages that facilitate database system design and use, and help improve performance.
Operators and maintenance personnel
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5. When Not to Use a DBMS overhead costs are too great
high initial investment
generality
overhead of security, concurrency control, recovery, integrity
Using Regular file:
data and applications are simple, well-defined, not expected to change
stringent real-time constraints
multi-user environment not needed
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6. Simplified Database System Environment
User/Programs
Database System
Application Programs/Queries
DBMS Software
Software to Process Queries/Programs
Software to Access Stored data
Stored Database Definition (Meta- Data)
Stored Database
Simplified Database System Environment
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7. Components of a DBMS Programmer User DBA DBMS Application Programs
Queries
Database
Schema
DBMS
DML
preprocessor
Query
processor
DDL
compiler
Program
object code
Database
manager
Dictionary
manager
Access
methods
File
manager
Database and
system catalog
System
buffers
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8. Database Manager: is a program module which provides the interface between the low-level data stored in the database and the application programs and queries submitted to the system.
Responsibility:
Interaction with the file manager: storing, retrieving and updating of data in the database
Integrity enforcement: checking for conditions.
Security enforcement: enforcing constraints on the users.
Backup and recovery:
Concurrency Control
File manager: It may be a general purpose file system provided by the underlying OS or it may be a specialized file system that knows about the particular ways in which the data of the database is stored. Which manages the allocation of space on the disk storage and the data structure used to represent information stored on the disk.
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9. Implications of the database Approach
Standards enforcement:
DBA can enforce standard naming conventions, etc
Reduced application development time:
adding new functionality to an existing database is “easy”
Flexibility:
adding new data and making some types of changes is “easy”
Up-to-date information: due to sharable characteristic
economies of scale: due to sharable resources the whole organization can make one investment
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10. Example: University Database
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