DATABASE EVOLUTION & ENVIRONMENT Chandra S. Amaravadi

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

IN THIS DISCUSSION Evolution The database approach Database architecture DBMS architecture DBMS environment

DBMS EVOLUTION

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 EVOLUTION OF DBMS DBMS evolved out of file processing environment:

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

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

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.

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

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

EVOLUTION OF DBMS.. (FYI)

THE DBMS/DB APPROACH

cust. emp. Enterprise Entity classes Data model Cust. Emp. Data base

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

GETTING INFORMATION FROM A DATABASE

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

GETTING INFORMATION IN DATABASE APPROACH Reports Queries [SQL, QBE] Forms Data from the database can be obtained through: “Views”

GETTING INFORMATION IN DATABASE APPROACH ACCT LOAN How can we get Acct & Loan info. in one report? ACCT #NAMEDT. OPENEDBALANCE 8895Moody4/16/11$35, Leak4/22/13$ Boring1/10/15$2000 LIDAMOUTINT. RATEBALANCE 9978$6,0006.0%$2, $5,0007.1%$5, $1,0008.5%$400

GETTING INFORMATION FROM MULTIPLE TABLES Rules for multi-table Select 1.In the Select part, precede each attribute name by name of table e.g. Select Acct.name, Loan.LID 2.In the From part, list tables separated by commas. 3.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. When data is retrieved from multiple tables, the following are the rules for writing queries:

DATABASE & DBMS ARCHITECTURE

THREE-SCHEMA ARCHITECTURE 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 An architecture for databases introduced by ANSI/SPARC*

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

THE THREE FORMS OF DATA.. l External/ --- The view of data as seen by a user/ application program (views). l Conceptual/ --- The view as seen by a database designer (base table) l 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.

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

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

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

D B M S Kernel MAJOR COMPONENTS OF DBMS Export/Import Data Defn. Data Defn. SQL Prog. Language Interface Prog. Language Interface Data Diction- ary Data Diction- ary Screen/ Report Gen. Screen/ Report Gen. Appln. Gen. Appln. Gen.

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.

THE DIFFERENT CLASSES OF USERS IN A DBMS UsersDevelopers Administrators DBMS

Data Administration DBMSClientDBMSClient LegacyApplicationsLegacyApplicationsEnterpriseApplicationsEnterpriseApplications DBMS/SQL Server AN INTEGRATED DATABASE ENVIRONMENT Developers End Users Dir.Server Database

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 COMPONENTS OF AN INTEGRATED DATABASE ENVIRONMENT

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

Data Warehouse OLAP Decisions Data Mining Internal Database Internal Database External Database DATA WAREHOUSES, OLAP & DATA MINING 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. Business Intelligence

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? DISCUSSION