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DATABASE EVOLUTION & ENVIRONMENT

DATABASE EVOLUTION & ENVIRONMENT. Chandra S. Amaravadi. PREVIOUSLY, IN INTRODUCTION. In our introduction we discussed the following:. Database importance Basic data organization concepts Database concept Development cycle Example application. IN THIS DISCUSSION. Evolution

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DATABASE EVOLUTION & ENVIRONMENT

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  1. DATABASE EVOLUTION & ENVIRONMENT Chandra S. Amaravadi

  2. PREVIOUSLY, IN INTRODUCTION In our introduction we discussed the following: • Database importance • Basic data organization concepts • Database concept • Development cycle • Example application

  3. IN THIS DISCUSSION • Evolution • The database approach • Database architecture • DBMS architecture • DBMS environment

  4. DBMS EVOLUTION

  5. EVOLUTION OF DBMS DBMS evolved out of file processing environment: • Introduction of business computers in 1950’s, ‘60’s • Used in TP applications (file processing) • Led to problems of file processing (see next) • Academic formulations of DBMS concepts • Standardization of DBMS concepts (by CODASYL 1971) • Hierarchical and network databases

  6. FILE PROCESSING APPROACH File processing evolved from transaction environment of the 1950’s. It involves application managing its own files. Application1 Application2 File1 File2

  7. EVOLUTION OF DBMS.. Following are the problems caused by file processing: • Uncontrolled redundancy • Program data dependence • Program maintenance • Poor data quality • Inability to get reports • Application backlog

  8. EVOLUTION OF DBMS.. PROBLEMS CAUSED BY FILE PROCESSING Uncontrolled redundancy – Same data is duplicated in multiple files Program data dependence – Application programs dependent on structure of the data Program maintenance – Too much effort spent in changing programs to accommodate changes in file structures. Poor data quality – Redundancy can often lead to inconsistent updates of the data, leading in turn to problems of data quality. Inability to get reports – Since each file was tied to a particular program, it was hard to get reports involving multiple files Application backlog – Managers’ requests for report led application programmers to write new applications to fulfill the request. They were typically behind in fulfilling the requests, hence the backlog.

  9. FROM FILE PROCESSING TO DBMS.. Applications Applications Application + Data management DBMS File handling routines Files Files Files

  10. EVOLUTION OF DBMS.. (FYI) Developments in DBMS include: Codd’s Paper In 1970 Ingres in 1971 Oracle in 1977 Britton Lee Founded in 1979 Teradata corp. Sybase in 1986 SAP

  11. EVOLUTION OF DBMS.. (FYI)

  12. THE DBMS/DB APPROACH

  13. THE DBMS/DB APPROACH Entity classes Emp. cust. Cust. emp. Data base Enterprise Data model

  14. THE DBMS/DB APPROACH • Integrated conceptualization of the data (??) • Organized design of database • Centralized management of data • System controlled access • Checks on data quality • Retrieve data easily (reports, queries) Application Application Application1 Application2 DBMS File1 File2 Files

  15. GETTING INFORMATION FROM A DATABASE

  16. GETTING INFORMATION IN FILE PROCESSING CROSS REFERENCE REPORT CUSTOMER ACCTS. LOANS ACCT. DATA LOAN DATA

  17. GETTING INFORMATION IN DATABASE APPROACH Data from the database can be obtained through: • Reports • Queries [SQL, QBE] • Views [forms that display]

  18. GETTING INFORMATION IN DATABASE APPROACH ACCT How can we get Acct & Loan info. in one report? LOAN

  19. GETTING INFORMATION FROM MULTIPLE TABLES Two rules for multi-table SQL When data is retrieved from multiple tables, the following are the rules for writing queries: • In the Select part, precede each attribute name by name of table e.g. Select Acct.name, Loan.LID • In the Where part, equate values of common key from both tables e.g. ..where Acct.Acct# = Loan.Acct# Write a query to list Name, balance, loan amt and balance for all customers.

  20. DATABASE & DBMS ARCHITECTURE

  21. THREE-SCHEMA ARCHITECTURE An architecture for databases introduced by ANSI/SPARC* • A prescription for how data should be stored (in a macro sense) • Provides benefits of logical and physical independence • Lacking in file processing approach *Standards Planning and Requirements Committee

  22. THE THREE FORMS OF DATA External (view) Conceptual/ Base table (schema) 11101001 111000110 Internal/ Hardware level (file organization) 11101001

  23. THE THREE FORMS OF DATA.. • External/ --- The view of data as seen by a user/ application program (views). • Conceptual/ --- The view as seen by a database designer (base table) • Internal --- The view of data as it is stored internally These three levels provide logical and physical data independence, the ability to change the structure of the data and the ability to change the internal storage structure, independently of the application program.

  24. THREE-SCHEMA ARCHITECTURE.. External View2 View1 Base Table Base Table Base Table Conceptual/ Logical Physical/ Internal Data is organized at three levels to provide logical/physical ______ ________________.

  25. THREE-SCHEMA ARCHITECTURE.. • Basic concept is that of a view • A view is the way data is presented • It is a subset of the data • The data resides in base tables • A base table contains information about an Eclass • Applns. access data via views • Views are created in SQL or by forms/reports

  26. THE THREE TYPES OF MODELS Create view Drop view External Views Conceptual Create table Alter table Schemas File Organizations Create index drop index Internal Models DBMS Facilities ___________ , ___________ and ____ __________ are examples of models corresponding to the three levels of the three schema architecture.

  27. Major Components of DBMS D B M S Kernel Data Defn. SQL Prog. Language Interface Data Diction- ary Screen/ Report Gen. Appln. Gen. D B M S Kernel Export/Import

  28. DBMS COMPONENTS.. Data definition – the facility through which schema is defined. (how new tables are created). SQL interface – the facility through which SQL commands are typed in. Programming language interface – the facility which processes SQL commands embedded in application program. Also known as the host language interface. Data dictionary – the facility that records details about the schema, reports, data entry forms etc. Screen & reports- the facility through which data entry screens and reports are created. Appln. Generation- the facility through which applications are created. Export/Import -- the facility through which files can be imported/exported in different DBMS formats. DBMS Kernel -- the actual programs which interact with the O/S and carry out data I/O. ODBC -- Open Database Connectivity – middleware to take SQL commands & return data.

  29. THE DIFFERENT CLASSES OF USERS IN A DBMS Developers Users Administrators DBMS

  30. An integrated database environment Data Administration Developers End Users Legacy Applications Enterprise Applications DBMS Client Database DBMS/SQL Server Dir. Server

  31. Components of an integrated database environment Directory server- a component that stores user names & PW (aka active directory or LDAP). DBMS client- a front end to provide access to DBMS functionality. Enterprise applications- various information systems of the organization. Legacy applications – older, mainframe-based applications. DBMS Server - a DBMS that can run queries (does not have user interface, only program interface). Database- collection of information

  32. DIFFERENT TYPES OF ENTERPRISE DATABASE ENVIRONMENTS SINGLE USER Single tier, single user, direct DBMS access CLIENT Two tier, multi-user, client server SERVER CLIENT three tier, multi-user, client server with middleware Middleware SERVER

  33. DATA WAREHOUSES, OLAP & DATA MINING Internal Database OLAP Data Warehouse Decisions Internal Database Data Mining Business Intelligence External Database Data warehousing refers to the use of high speed/high capacity servers to store historical data and to make this available to decision makers. OLAP is the process of analyzing historical data on a PC using mult-dimensional databases (i.e. non-relational databases) using aggregate data operations. Data mining refers to identification of patterns from data.

  34. DISCUSSION • What organization standardized DBMS concepts? • Who was the chief architect of relational systems? • What data-related functions were performed in the file processing approach? • What are some of the basic features of a DBMS? • What is the smallest unit of data in a database? • Define the terms: schema, view, database, three-schema architecture. • How is redundancy minimized in the database approach? • What are advantages of the 3-schema architecture? • What is the difference between 2-tier & 3-tier environments?

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