Databases & Database Users Flashcards
A collection of related data.
Database
Properties of Databases
- Represents an aspect of the real world (a.k.a. miniworld)
- Logically coherent collection of data with some inherent meaning
- Designed, built, & populated with data for a specific purpose
- Can be of any size & complexity
- Generated and maintained manually or it may be computerized
A computerized system that enables users to create and maintain a database.
Database Management System (DBMS)
A general-purpose software system that facilitates the processes of defining, constructing, manipulating, and sharing databases among various users and applications
Database Management System (DBMS)
Functions of a DBMS
- Defining a database
- Constructing a database
- Manipulating a database
- Protecting a database
- Maintaining a database
Specifying data types, structures, and constraints of the data to be stored in the database.
Defining a Database
Data within the Data (data about the data)
Stored Database Definition
Metadata
Process of storing the data on some storage medium that is controlled by the DBMS.
Constructing a Database
Querying the database to retrieve specific data, updating the database to reflect changes, and generate reports.
Manipulating a Database
Query vs Transaction
Query ➔ fetch data from database (no changes)
Transaction ➔ may cause some data to be written/changed
Protecting a database against against hardware or software malfunction (e.g. crashes)
System Protection
Protecting a database against unauthorized or malicious access
Security Protection
Allowing the system to evolve as requirements change over time
Maintaining a Database
Database + DBMS
Database System
Complete definition/description of database structure and constraints
Self-Describing Nature of a Database System
Ability to make changes in database structure without the need to make changes to accessing programs
Program-Data independence
Process of hiding data storage and implementation details with purpose of achieving data independence
Data Abstraction
Provides facilities for defining multiple views since database system is multiuser and used by variety of distinct applications.
Support of Multiple View of Data
subset of the database or virtual data (derived) with purpose of presenting a different perspective of the database
View
Database System Characteristics
- Self-describing nature of a database system
- Insulation between programs and data, and data abstraction
- Support of multiple views of the data
- Sharing of data and multiuser transaction processing
Allows multiple users to access the database at the same time
Includes concurrency control to ensure that several users trying to update the same data do so in a controlled manner so that the change result is correct
Sharing of Data & Multiuser Transaction Processing
Advantages of Database System
- Controlling redundancy
- Restricting Unauthorized Access
- Provide Persistent Storage for Program Objects
- Providing Storage Structures and Search Techniques for Efficient Query Processing
- Providing Backup and Recovery
- Providing Multiple User Interfaces
- Representing Complex Relationships among Data
- Enforcing Integrity Constraints
- Permitting Inferencing and Actions Using Rules and Triggers
- Potential for Enforcing Standards
- Reduced Application Development Time
- Flexibility
- Availability of Up-to-Date Information
- Economies of Scale
When not to use a database system
- Simple, well-defined database application that are not expected to change at all
- Stringent, real-time requirements for some application programs that may not be met because of DBMS overhead
- Embedded systems with limited storage capacity, where a general-purpose
DBMS would not fit - No multiple-user access to data
Responsible for authorizing access to the database, coordinating, and monitoring the use and acquisition of software and hardware resources
Database Administrators (DBAs)
