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Information about Overview-DBMS

Published on July 19, 2010

Author: jesuscharles

Source: authorstream.com

Database Management Systems : Database Management Systems By Dinesha L Lecturer, Dept. Of CSE SSIT, Tumkur Chapter-1 Objectives : Objectives An Overview of Database Management Database DBMS Database Systems Why Use Database Database Architecture An Example of the Three Levels Schema Data Independence Types Of Database Models Database Design Phases Slide 3: Definitions: Data: Known facts that can be recorded and that have implicit meaning Database: Collection of related data Ex. the names, telephone numbers and addresses of all the people you know Database Management System: A computerized record-keeping system Slide 4: Goals of a Database Management System: To provide an efficient as well as a convenient environment for accessing data in a database Enforce information security: database security, concurrency control, crash recovery It is a general purpose facility for: Defining database Constructing database Manipulating database History of DBMS : History of DBMS 1960 – First DBMS designed by Charles Bachman at GE. IBMs Information Management System (IMS) 1970 – Codd introduced the RDBMS 1980 – Relational model became popular and accepted as the main database paradigm. SQL, ANSI SQL, etc. 1980 to 1990 – New data models, powerful query languages, etc. Popular vendors are Oracle, SQL Server, IBMs DB2, Informix, etc. Slide 6: Various types of data: Images, Text, complex queries, Data Mining, etc. Enterprise Resource Planning (ERP) Management Resource Planning (MRP) Database in Web technologies Current Database trends: Multimedia databases Interactive video Streaming data Digital Libraries DBMS Functions : DBMS Functions Data Definition Data Manipulation Data Security and Integrity Data Recovery and Concurrency Data Dictionary Performance Early File Systems Vs DBMS : Early File Systems Vs DBMS Catalog in DBMS. Data definition in file systems is part of application programs. Program-Data independence Views Sharing and Transaction processing Slide 9: Database File System approach DBMS approach Slide 10: Redundancy can be reduced Inconsistency can be avoided Data can be shared Standards can be enforced Security restrictions can be applied Integrity can be maintained Data independence can be provided Backup and Recovery Benefits of database approach Describing and Storing Data in DBMS : Describing and Storing Data in DBMS Data Model A data model is a collection of high-level data description constructs that hide many low-level storage details. Relational Data Model Semantic Data Model – ER Model Relational Model : Relational Model A Relation is a set of records and attributes. Also known as tuples and columns. A Schema is the description of data in terms of a data model. Eg. Student(RegNo : String, Name : String, Sem : Integer, Branch : String) Student Relation : Student Relation RegNo Name Sem Branch 0016 N. Deepak 3 CSE 0674 K. Gopal 5 MECH 2901 Kanchana 2 CSE Other Data Models : Other Data Models Relational Model – DB2, Oracle, Informix, Sybase, MS-Access, Foxbase, Paradox, etc. Hierarchical Model – IMS DBMS Network Model – IDS & IDMS Object-Oriented Model – ObjectStore & Versant Object-Relational Model – Products from IBM, Oracle, ObjectStore, Versant. Three-Layer Abstraction : Three-Layer Abstraction Physical Schema Conceptual Schema External Schema - 2 External Schema - 1 External Schema - 3 Disk Conceptual Schema : Conceptual Schema Describes the stored data in terms of the data model of the DBMS. This leads to conceptual database design. Example: Student(RegNo:Integer, Name:String, Sem:Integer, Branch:String) Faculty(Fid:Integer, FName:String, Salary:Float) Course(CourseNo:Integer, CName:String, Credit:Integere, Dept:String) Section(SecId:Integer, CourseNo:Integer, Sem:Integer, Year:Integer, Instructor:String) GradeReport(RegNo:Integer, SecId:Integer, Grade:Char) Physical Schema : Physical Schema Describes the actual storage details of the relations described in conceptual schema. Primary indexing, sequential, binary, secondary indexing, etc. This leads to the physical database design. External Schema : External Schema Describes several views of the database based on the database model. Several external schemas are possible for a single database. Each view is based upon the user requirements. Example: StdGrade(RegNo:Integer, Name:String, Sem:Integer, Grade:Char) Program-Data Independence : Program-Data Independence The data independence is the ability to change the schema at one level of a database system with out changing the schema at a higher level. Logical data Independence It is the ability to change the schema at one level of a database system without changing the external schema or application programs, is called as the logical data independence. With out changing the application programs, one can change the logical schema. Slide 20: Example Suppose the Faculty relation is modified as: Faculty_Public(Fid:Integer, FName:String, Office:Integer) Faculty_Private(Fid:Integer, Salary:Float) Any view designed before this modification can still retrieve the data with little modification (relation name) and obtain the same answer. Slide 21: Physical data independence There are occasions for changing the internal structures for improved performance of the retrieval of data. Any change introduced to the internal schema or physical schema will not affect the other schemas. Database Languages : Database Languages DDL – Data Manipulation Language SDL – Storage Definition Language VDL – View Definition Language DML – Data Manipulation Language (For data manipulations like insertion, deletion, update, retrieval, etc.) Transaction Management : Transaction Management Atomic operation – Handling concurrent execution of transactions from several users. Example: Reservation systems, Banking systems. Transaction failures and recovery. Locking protocols. Log (WAL – Write Ahead Log) DBMS Architecture : DBMS Architecture Slide 25: Plan Executor Optimizer Operator Evaluator Parser SQL Engine Recovery Manager Lock Manager Tx Manager Files & Access Buffer Manager Disk Space Manager DBMS Catalog Data File Database Web Forms Front-End SQL I/f SQL Commands People Who Work with Databases : People Who Work with Databases Database Implementers End Users Application Programmers DBA End Users : End Users Casual users These are people who use the database occasionally. Naive users These are users who constantly querying and updating the database. Eg. Reservation Clerks of Airline, Railway, Hotel, etc. Clerks at receiving station of Courier service, Insurance agencies, etc. Sophisticated Users People who use for their complex requirements. Eg. Engineers, Scientists, Business analysts… Standalone Users Who maintain database for personal use. DBA : DBA Managing resources Creation of user accounts Providing security and authorization Managing poor system response time System Recovery Tuning the Database Slide 29: End of Chapter - 1

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