Database Management Systems

Transcription

1 DATABASE CONCEPTS & APPLICATIONS Database Management Systems A Database Management System (DBMS) is a software package designed to store and manage databases through database applications. User Database Application(s) DBMS Database User 2 ١

2 Personal o Files-based, dbase, Paradox, Access Multi Multi-User/Client User/Client-Server/Web Server/Web-Based o Oracle, DB2, Ingris, Sybase Personal Web-Based o MySQL Non Non-Relational o Object-Oriented Databases 3 Data Independence o Applications insulated from how data is structured and stored. o Application programs should not be exposed to details of data representation and storage The DBMS provides an abstract view of the data Efficient Data Access o A DBMS utilizes sophisticated techniques to store and retrieve data 4 ٢

3 Data Integrity and Security o A DBMS can enforce integrity constraints o A DBMS can enforce access controls that govern what data is visible to different classes of users Concurrent Access and Crash Recovery o A DBMS schedules data access among various users o A DBMS protects against system failures 5 Reduced Application Development Times o A DBMS supports important data access functions that are common to many applications o A DBMS supports high-level interface to the data o DBMS applications are more robust No need for debugging and testing 6 ٣

4 A A DBMS is complex o Cost of DBMS o Additional hardware costs o Cost of conversion o Higher impact of a failure Performance not adequate for certain applications o Examples: Real-time constraints Critical constraints (need special custom code) Applications may need to manipulate data in ways not supported by the query language 7 8 ٤

5 Hardware Can range from a PC to a network of computers. Software DBMS, operating system, network software (if necessary) and also the application programs. Data Used by the organization and a description of this data called the schema. 9 Procedures Instructions and rules that should be applied to the design and use of the database and DBMS. People End-User Database Administrator (DBA) Application Developer. etc 10 ٥

6 Database Database Contains Users Data Metadata Indexes & Other System Data Application Metadata D B M S E n g i n e Design Tools Table Creation Tools Form Creation Tools Query Creation Tools Report Creation Tools Procedural Language Compiler Run Time Form Processor Query Processor Report Writer Procedural Language Run Time Application Programs Application Programs Developer Users 11 The Design Tools o Each DBMS comes with a set of tools to help in creating tables, forms, reports, queries, etc. o Design tools also allow users more control through the use of programming language interfaces. 12 ٦

7 The Runtime Facilities o Developers design forms, reports, and queries. However, they contain no data. The DBMS Runtime facilities are responsible for retrieving the relevant data from the database and displaying it in the form, report, or query. 13 The DBMS Engine o The DBMS Engine has direct access to the physical database. Requests sent to the database (in the form of tables, rows, and columns) are intercepted by the DBMS Engine and sent to the operating system in terms of files and file offsets. o The DBMS Engine is also responsible of transaction management, locking, and backup and recovery. 14 ٧