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Note for Database Management System - DBMS By ananthi

  • Database Management System - DBMS
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  • Computer Science Engineering
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Introduction to DBMS

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Database Management System (DBMS) DBMS is collection of interrelated data stored in organized manner. Database Applications: Banking: transactions Airlines: reservations, schedules Universities: registration, grades Sales: customers, products, purchases Online retailers: order tracking, customized recommendations Manufacturing: production, inventory, orders, supply chain Human resources: employee records, salaries, tax deductions Databases can be very large.

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Drawbacks of file systems Data redundancy and inconsistency Multiple file formats, duplication of information in different files Difficulty in accessing data Need to write a new program to carry out each new task Data isolation Multiple files and formats Integrity problems Integrity constraints (e.g., account balance > 0) become “buried” in program code rather than being stated explicitly Hard to add new constraints or change existing ones Atomicity of updates Failures may leave database in an inconsistent state with partial updates carried out

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Drawbacks of file systems (Cont.) Concurrent access by multiple users Concurrent access needed for performance Uncontrolled concurrent accesses can lead to inconsistencies  Example: Two people reading a balance (say 100) and updating it by withdrawing money (say 50 each) at the same time Security problems

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