Database systems
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This chapter introduces database systems and their advantages over traditional file systems. It discusses the components of a database system including the database, database management system (DBMS), and their roles in data storage and access. Databases have evolved from file systems to address issues like data redundancy, inconsistency, and dependence on structure and storage characteristics. The chapter outlines different types of databases and the importance of database design. It provides examples of problems in traditional file system data management to illustrate improvements made by modern database systems.
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Database systems
- 1. Database Systems: Design, Implementation, and Management Eighth Edition Chapter 1 Database Systems
- 2. Database Systems, 8th Edition 2 Objectives • The differences between data and information • What a database is • What the various types of databases are • Why they are valuable assets for decision making • The importance of database design
- 3. Database Systems, 8th Edition 3 Objectives (continued) • How modern databases evolved from file systems • About flaws in file system data management • What the database system’s main components are • How a database system differs from a file system • The main functions of a database management system (DBMS)
- 4. Database Systems, 8th Edition 4 Introduction • Good decisions require good information derived from raw facts • Data managed most efficiently when stored in a database • Databases evolved from computer file systems • Understanding file system characteristics is important
- 5. Database Systems, 8th Edition 5 Data vs. Information • Data are raw facts • Information is the result of processing raw data to reveal meaning • Information requires context to reveal meaning • Raw data must be formatted for storage, processing, and presentation • Data are the foundation of information, which is the bedrock of knowledge
- 6. Database Systems, 8th Edition 6 Data vs. Information (continued) • Data: building blocks of information • Information produced by processing data • Information used to reveal meaning in data • Accurate, relevant, timely information is the key to good decision making • Good decision making is the key to organizational survival
- 7. Database Systems, 8th Edition 7 Introducing the Database and the DBMS • Database: shared, integrated computer structure that stores a collection of data – End-user data: raw facts of interest to the end user – Metadata: data about data • Metadata provides description of data characteristics and relationships in data – Complements and expands value of data • Database management system (DBMS): collection of programs – Manage structure and control access to data
- 8. Database Systems, 8th Edition 8 Role and Advantages of the DBMS • DBMS is the intermediary between the user and the database • Database structure stored as file collection • Access database through the DBMS • DBMS enables data to be shared • DBMS integrates many users’ views of the data
- 10. Database Systems, 8th Edition 10 Role and Advantages of the DBMS (continued) • 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
- 11. Database Systems, 8th Edition 11 Types of Databases • Databases can be classified according to: – Number of users – Database location(s) – 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 database supports a small number – Enterprise database supports a large number
- 12. Database Systems, 8th Edition 12 Types of Databases (continued) • 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
- 13. Database Systems, 8th Edition 13 Types of Databases (continued) • Unstructured data exist in their original state • Structured data result from formatting – Structure applied based on type of processing to be performed • Semistructured data have been processed to some extent • Extensible Markup Language (XML) represents data elements in textual format • XML database supports semistructured XML data
- 15. Database Systems, 8th Edition 15 Why Database Design is Important • Database design focuses on design of database structure used for end-user data – Designer must identify database’s expected use • Well-designed database: – Facilitates data management – Generates accurate and valuable information • Poorly designed database: – Causes difficult-to-trace errors
- 16. Database Systems, 8th Edition 16 Historical Roots: Files and File Systems • Reasons for studying file systems: – Complexity of database design easier to understand – Understanding file system problems helps to avoid problems with DBMS systems – Knowledge of file system useful for converting file system to database system • File systems typically composed of collection of file folders, each tagged and kept in cabinet – Organized by expected use
- 17. Database Systems, 8th Edition 17 Historical Roots: Files and File Systems (continued) • Contents of each file folder logically related • Manual system served as a data repository for small data collections – Cumbersome for large collections • Data processing (DP) specialist converted computer file structure from manual system – Wrote software that managed the data – Designed the application programs • Initially, computer files systems resembled manual systems
- 18. Database Systems, 8th Edition 18 Historical Roots: Files and File Systems (continued) • As number of files increased, file systems evolved – Each file used its own application program to store, retrieve, modify data – Each file owned by individual or department that commissioned its creation • Data processing (DP) manager supervised the DP department • DP department’s primary activity remained programming
- 19. Database Systems, 8th Edition 19 FIELD RECORD : a logically connected set of one or more fields that describe person, place or thing
- 22. Database Systems, 8th Edition 22 Problems with File System Data Management • File system 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
- 23. Database Systems, 8th Edition 23 Problems with File System Data Management (continued) • Security features difficult to program – Often omitted in file system environments • Summary of file system limitations: – Requires extensive programming – Can not perform ad hoc queries – System administration complex and difficult – Difficult to make changes to existing structures – Security features likely to be inadequate
- 24. Database Systems, 8th Edition 24 Structural and Data Dependence • Structural dependence: access to a file dependent on its own structure – All file system programs must be modified to conform to a new file structure • Structural independence: change file structure without affecting data access • Data dependence: data access changes when data storage characteristics change • Data independence: data storage characteristics do not affect data access penggunaan sistem yang merubah struktur capaian data. Contoh: keluarkan duit Tabung Haji cara manual dan juga dengan menggunakan ATM. perubahan tidak menjejaskan capaian data cara capaian data berubah apabila data berubah perubahan data tidak menjejaskan cara capaian data
- 25. Database Systems, 8th Edition 25 Structural and Data Dependence (continued) • Practical significance of data dependence is difference between logical and physical format • Logical data format: how human views the data • Physical data format: how computer must work with data • Each program must contain: – Lines specifying opening of specific file type – Record specification – Field definitions
- 26. Database Systems, 8th Edition 26 Field Definitions and Naming Conventions • Storing customer name as single field is a liability – Better record definition breaks fields into component parts • Selecting proper field names important; field names are descriptive – With proper naming conventions, file structure becomes self-documenting – Some software places restrictions on length of field names • Each record should have unique identifier
- 28. Database Systems, 8th Edition 28 Data Redundancy • File system structure makes it difficult to combine data from multiple sources – Vulnerable to security breaches • Organizational structure promotes storage of same data in different locations – Islands of information • Data stored in different locations unlikely to be updated consistently • Data redundancy: same data stored unnecessarily in different places
- 29. Database Systems, 8th Edition 29 Data Redundancy (continued) • Data inconsistency: different and conflicting versions of same data occur at different places • Data anomalies: abnormalities when all changes in redundant data not made correctly – Update anomalies – Insertion anomalies – Deletion anomalies
- 30. Database Systems, 8th Edition 30 Database Systems • Database system consists of logically related data stored in a single logical 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, access paths – Takes care of defining, storing, managing all access paths and components
- 32. Database Systems, 8th Edition 32 The Database System Environment • Database system: defines and regulates the collection, storage, management, use of data • Five major parts of a database system: – Hardware – Software – People – Procedures – Data
- 34. Database Systems, 8th Edition 34 The Database System Environment (continued) • 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
- 35. Database Systems, 8th Edition 35 The Database System Environment (continued) • Procedures: instructions and rules that govern the design and use of the database system • Data: the collection of facts stored in the database • Database systems created and managed at different levels of complexity • Database solutions must be cost-effective as well as tactically and strategically effective • Database technology already in use affects selection of a database system
- 36. Database Systems, 8th Edition 36 DBMS Functions • Most functions transparent to end users – Can only be achieved through the DBMS • Data dictionary management – DBMS stores definitions of data elements and relationships (metadata) in a data dictionary – DBMS looks up required data component structures and relationships – Changes automatically recorded in the dictionary – DBMS provides data abstraction, removes structural and data dependency ciri ciri kepada sesuatu data
- 38. Database Systems, 8th Edition 38 DBMS Functions (continued) • 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: activities that make the database perform more efficiently – DBMS stores the database in multiple physical data files
- 40. Database Systems, 8th Edition 40 DBMS Functions (continued) • 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.
- 41. Database Systems, 8th Edition 41 DBMS Functions (continued) • 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
- 42. Database Systems, 8th Edition 42 DBMS Functions (continued) • Data integrity management – DBMS promotes and enforces integrity rules • Minimizes redundancy • Maximizes consistency – Data relationships stored in data dictionary used to enforce data integrity – Integrity especially important in transaction- oriented database systems
- 43. Database Systems, 8th Edition 43 DBMS Functions (continued) • Database access languages and application programming interfaces – DBMS provides access through a query language – Query language is a nonprocedural language – Structured Query Language (SQL) is the de facto query language • Standard supported by majority of DBMS vendors
- 44. Database Systems, 8th Edition 44 DBMS Functions (continued) • Database communication interfaces – Current DBMSs accept end-user requests via multiple different network environments – Communications accomplished in several ways: • End users generate answers to queries by filling in screen forms through Web browser • DBMS automatically publishes predefined reports on a Web site • DBMS connects to third-party systems to distribute information via e-mail
- 45. Database Systems, 8th Edition 45 Managing the Database System: A Shift in Focus • Database system provides a framework in which strict procedures and standards enforced – Role of human changes from programming to managing organization’s resources • Database system enables more sophisticated use of the data • Data structures created within the database and their relationships determine effectiveness
- 46. Database Systems, 8th Edition 46 Managing the Database System: A Shift in Focus (continued) • Disadvantages of database systems: – Increased costs – Management complexity – Maintaining currency – Vendor dependence – Frequent upgrade/replacement cycles
- 47. Database Systems, 8th Edition 47 Summary • Data are raw facts • Information is the result of processing data to reveal its meaning • Accurate, relevant, timely information is the key to good decision making • Data usually stored in a database • DBMS implements a database and manages its contents
- 48. Database Systems, 8th Edition 48 Summary (continued) • Metadata is data about data • Database design defines the database structure – Well-designed database facilitates data management, generates valuable information – Poorly-designed database leads to bad decision making, organizational failure • Databases evolved from manual and computerized file systems – In a file system, data stored in independent files • Each requires its own management program
- 49. Database Systems, 8th Edition 49 Summary (continued) • Some limitations of file system data management: – Requires extensive programming – System administration complex and difficult – Changing existing structures difficult – Security features likely inadequate – Independent files tend to contain redundant data • Structural and data dependency problems
- 50. Database Systems, 8th Edition 50 Summary (continued) • Database management systems developed to address file system’s inherent weaknesses • DBMS present database to end user as single repository – Promotes data sharing – Eliminates islands of information • DBMS enforces data integrity, eliminates redundancy, promotes security