evolution of database management system
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Introduction to Database Introduction to Database Management SystemManagement System
The Traditional Approach To Data The Traditional Approach To Data ManagementManagement
– Create new files for each application
– Data redundancy
– Data integrity
Disadvantages of File ProcessingDisadvantages of File Processing
• Program-Data Dependence– All programs maintain metadata for each file they
use• Data Redundancy (Duplication of data)
– Different systems/programs have separate copies of the same data
• Limited Data Sharing– No centralized control of data
• Lengthy Development Times– Programmers must design their own file formats
• Excessive Program Maintenance– 80% of of information systems budget
Components of the database environment
Components of theComponents of theDatabase EnvironmentDatabase Environment
• CASE Tools – computer-aided software engineering• Repository – centralized storehouse of metadata• Database Management System (DBMS) – software
for managing the database• Database – storehouse of the data• Application Programs – software using the data• User Interface – text and graphical displays to users• Data Administrators – personnel responsible for
maintaining the database• System Developers – personnel responsible for
designing databases and software• End Users – people who use the applications and
databases
Disadvantages of DBMSDisadvantages of DBMS
• Databases used in enterprises may involve additional risks as compared to a conventional data processing system in some areas
• Confidential, Privacy and Security : When information is centralized and is made available to users from remote locations, there is a possibility of unauthorized users accessing sensitive information.
• It is necessary to take technical, administrative and legal measures.
Disadvantages of DBMSDisadvantages of DBMS
• Data Quality : Since database is accessible to users remotely, adequate controls are needed to control users updating data and to control data quality.
• With increased number of users accessing directly, there is an opportunity for users to damage data.Unless there are suitable controls, the data quality may be compromised.
• Data Integrity : Since a large number of users cloud be using a database concurrently, technical safeguards are necessary to ensure that data remain correct during operation.
Overall System Structure Overall System Structure
Overall System StructureOverall System Structure
• A database system is partitioned into modules which handles different responsibilities of over all system.
The functional components of a database system are
Query processor ComponentStorage manager component
Query Processor ComponentQuery Processor Component
• DML Compiler : It translates DML statements into a lower level instructions that the query evaluation engine understands
• Embedded DML precompiler : It converts DML statements embedded in an application program into normal procedure calls in the host language.
• DDL Interpreter : It interprets DDL statements and records them in a set of tables
• Query evaluation engine : It executes lower level instructions generated by the DML compiler
Storage manager componentStorage manager component
• It is an Interface between the data stored in the database and the application programs and queries submitted to the system.
• Authorization and Integrity manager : It tests for satisfaction of integrity constraints and checks the authority of users to access data.
• Transaction Manager : It ensures concurrent transaction executions processed without conflicting.
• File manager : It manages the allocation of space on disk and the data structures used to represent information.
• Buffer manager : Which is responsible for fetching data from disk storage into main memory.
Application ArchitecturesApplication Architectures
Two-tier architecture: E.g. client programs using ODBC/JDBC to communicate with a databaseThree-tier architecture: E.g. web-based applications, and applications built using “middleware”