Exam 1-Chapter 1 Flashcards
Data
Raw facts and the building blocks of information
Information
the result of processing raw data to reveal meaning; produced by processing data; used to reveal meaning in data
Knowledge
Data are the foundation of information, which is the bedrock of knowledge
Metadata
Data about data; provides description of data characteristics and relationships in data; complements and expands value of data
Database Management System (DBMS)
Manages structure and controls access to data; intermediary between the user and the database; enables data to be shared; integrates many users’ views of the data
Advantages of a DBMS
Improved data sharing; Improved data security; Better data integration; Minimized data inconsistency; Improved data access; Improved decision making; Increased end-user productivity
Classifications of Databases
Number of users; Database locations; Expected type and extent of use
Single-User Database
Supports only one user at a time (desktop database: single-user; runs on PC)
Multiuser Database
Supports multiple users at the same time (workgroup and enterprise databases)
Centralized Database
Data located at a single site
Distributed Database
Data distributed across several different sites
Operational Database
Supports a company’s day-to-day operations (transactional or production database)
Data Warehouse
Stores data used for tactical or strategic decisions
Database Design
Focuses on design of database structure used for end-user data (designer must identify database’s expected use
Well-Designed Database/Poorly Designed Database
Well-design: (facilitates data management; generates accurate and valuable information)
Poorly designed datatbase: (causes difficult-to-trace errors; may lead to bad decision making)
Manual Systems
Served as a data repository for small data collections; cumbersome for large collections
Data Processing (DP) Specialist
Computerized file system; converted computer file structure from manual system; wrote software that managed the data; designed the application programs
Increaed Files
As number of files increased, file systems evolved; each file used its own applicaton program to store, retrieve, and modify data; each file was owned by individual or department that commissioned its creation
Problems with File System Data Processing
File systems were an improvement over manual system (file systems used for more than two decades; understanding the shortcomings of file systems aids in development of modern databases; many problems not unique to file systems)
Even simple file system retrieval task required extensive programming (ad hoc queries impossible;changing existing structure difficult)
Security features difficult to program (often omitted in file system environment)
Structural Dependence
Access to a file is dependent on its own structure (all file system programs must be modified to conform to a new file structure)
Structureal Indedependence
Change file structure without affecting data access
Data Dependence
Data access changes when data storage characteristics change (eg, changing a data type)
Data Independence
Data storage characteristics do not affect data access
Logical Data Format
How human views the data
Physical Data Format
How computer must work with data
Each Program Accessing a File System File Must Contain
Lines specifying opening of specific file type
Record specification
Field Definitions
Data Redundancy
Same data stored unnecessarily in different places (Having multiple copies of data=vulnerable to security breaches; Data stored in different locations is unlikely to be updated consistently)
Data Inconsistancy
Different and conflicting versions of same data occur at different places
Data Anomalies
Abnormalities when all changes in redundant data are not made correctly (update anomalies; insertion anomalies: cannot insert a fact about one entity without a fact about another entity; deletion anomaliies: if the customers are deleted we also lose the associated agent data)
Database Systems
Database systems consists of logically related data stored in a single locical data repository (may be physically distributed among multiple storage facilities; DBMS eliminates most of file system’s problems; current generation stores data structures, relationships between structures, and access paths)
Defines and regulates the collection, storage, management, and use of data
Database System Environment
Five major parts of a database system:
- Hardware
- Software
- People
- Procedures
- Data
Hardware
All the system’s physical devices
Software
Three types of software required:
- Operating system software
- DBMS software
- Application programs and utility software
People
All users of the database system (system and database administrators; database designers; systems analysts and programmers; end users)
Procedures
Instructions and rules that goven the design and use of the database system
Data
The collection of facts stored in the database
Data Dictionary Management
DBMS stores definitions of data elements and relationships (metadate in a data dictionary
DBMS looks up required data component structures and relationships
Changes automatically recorded in the dictionary
Do not have to modify all programs using the data and removes structural and data dependency
Data Storage Management
DBMS creates and manages complex structures required for data storage
Also stores related data entry forms, screen definitions, report definitions, etc
Performance Tuning
Actiivities that make the database perform more efficiently
Data Transformation and Presentation
DBMS transforms data entered to conform to required data structures
DBMS transforms physically retrieved data to conform to user’s logical expectations
Security Management
DBMS creates a security system that enforces user security and data privacy
Security rules determine which users can access the database, which items can be accessed, etc.
Multiuser Access Control
DBMS uses sophisticated algorithms to ensure concurrent access does not affect integrity
Backup and Recovery Management
DBMS provides backup and data recovery to ensure data safety and integrity
Recovery management deals with recovery of database after a failure (critical to preserving database’s integrity
Data Integrity Management
DBMS promotes and enforces integrity rules (minizes redundancy; maximizes consistency)
Data relationships stored in data dictionary used to enforce data integrity
Integrity is especially important in transaction-oriented database systems
Query Language
Nonprocedural language
Structured Query Language (SQL)
The de facto query language (standard supported by majority of DBMS vendors
Disadvantages of Database Systems
Increased costs: hardware, software, personal
Management complexity: DB interfaces with many other technologies; security must also be constantly assessed
Maintaining currency: software patches, security updates, personnel training
Vendor dependence
Frequent update/replacement cycles
