Files Vs DataBase


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Covers Unit IV of MBA UoM Syllabus

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Files Vs DataBase

  1. 1. File System vs. DBMS
  2. 2. Traditional Approach <ul><li>Applications developed in an ad-hoc and opportunistic manner </li></ul><ul><li>Data requirements for applications derived independently </li></ul><ul><li>Data files developed for individual applications </li></ul><ul><li>Application programs are data dependent </li></ul>
  3. 3. Files Dedicated to Application Programs
  4. 4. Database Approach <ul><li>Centralization of information management </li></ul><ul><li>Data shared by different groups of users and application programs </li></ul><ul><li>Provision of multiple interfaces </li></ul><ul><li>Representation of complex relationships between data </li></ul><ul><li>Integrity constraint handling </li></ul><ul><li>Advanced facilities for backup and recovery </li></ul>
  5. 5. Data Sharing in a Database Environment
  6. 6. Interacting with a Database
  7. 7. File System vs. DBMS <ul><li>A company has 500 GB of data on employees, departments, products, sales, & so on.. </li></ul><ul><li>Data is accessed concurrently by several employees </li></ul><ul><li>Questions about the data must be answered quickly </li></ul><ul><li>Changes made to the data by different users must be applied consistently </li></ul><ul><li>Access to certain parts of the data be restricted </li></ul>
  8. 8. File System vs. DBMS <ul><li>Data stored in operating system files </li></ul><ul><li>Many drawbacks!!! </li></ul><ul><ul><li>500 GB of main memory not available to hold all data. Data must be stored on secondary storage devices </li></ul></ul><ul><ul><li>Even if 500GB of main memory is available, with 32-bit addressing, we cannot refer directly to more than 4GB of data </li></ul></ul><ul><ul><li>Data redundancy and inconsistency </li></ul></ul><ul><ul><ul><li>Multiple file formats, duplication of information in different files </li></ul></ul></ul><ul><ul><li>Special program to answer each question a user may ask </li></ul></ul>
  9. 9. File System vs. DBMS <ul><li>Many drawbacks!!! </li></ul><ul><ul><li>Integrity problems </li></ul></ul><ul><ul><ul><li>Integrity constraints (e.g. account balance > 0) become “buried” in program code rather than being stated explicitly </li></ul></ul></ul><ul><ul><ul><li>Hard to add new constraints or change existing ones </li></ul></ul></ul><ul><ul><li>We must protect the data from inconsistent changes made by different users. If application programs need to address concurrency, their complexity increases manifolds </li></ul></ul><ul><ul><li>Consistent state of data must be restored if the system crashes while changes are being made </li></ul></ul><ul><ul><li>OS provide only a password mechanism for security. Not flexible enough if users have permission to access subsets of data </li></ul></ul>
  10. 10. File System vs. DBMS <ul><li>These drawbacks have prompted the development of database systems </li></ul><ul><li>Database systems offer solutions to all the above problems? </li></ul>
  11. 11. Advantages <ul><li>Sharing of data </li></ul><ul><li>Enforcement of security </li></ul><ul><li>Enforcement of development and maintenance standards </li></ul><ul><li>Reduction of redundancy </li></ul><ul><li>Avoidance of inconsistency across files </li></ul><ul><li>Maintenance of integrity </li></ul><ul><li>Data independence </li></ul><ul><li>Firm theoretical foundation (for the relational model) </li></ul>
  12. 12. Advantages of a DBMS <ul><li>Program-Data Independence </li></ul><ul><ul><li>Insulation between programs and data: Allows changing data storage structures and operations without having to change the DBMS access programs. </li></ul></ul><ul><li>Efficient Data Access </li></ul><ul><ul><li>DBMS uses a variety of techniques to store & retrieve data efficiently </li></ul></ul><ul><li>Data Integrity & Security </li></ul><ul><ul><li>Before inserting salary of an employee, the DBMS can check that the dept. budget is not exceeded </li></ul></ul><ul><ul><li>Enforces access controls that govern what data is visible to different classes of users </li></ul></ul>
  13. 13. Advantages of a DBMS <ul><li>Data Administration </li></ul><ul><ul><li>When several users share data , centralizing the administration offers significant improvement </li></ul></ul><ul><li>Concurrent Access & Crash Recovery </li></ul><ul><ul><li>DBMS schedules concurrent access to the data in such a manner that users think of the data as being accessed by only one user at a time </li></ul></ul><ul><ul><li>DBMS protects users from the ill-effects of system failures </li></ul></ul><ul><li>Reduced Application Development Time </li></ul><ul><ul><li>Many important tasks are handled by the DBMS </li></ul></ul>
  14. 14. Functions of a DBMS <ul><li>Data storage, retrieval, update </li></ul><ul><li>A user-accessible catalog </li></ul><ul><li>Transaction support </li></ul><ul><li>Concurrency control </li></ul><ul><li>Recovery services </li></ul><ul><li>Authorisation services </li></ul><ul><li>Support for data communication </li></ul><ul><li>Integrity services </li></ul><ul><li>Data independence </li></ul><ul><li>Utility services </li></ul>
  15. 15. Databases Everywhere!!! <ul><li>DBMS contains information about a particular enterprise </li></ul><ul><ul><li>Collection of interrelated data </li></ul></ul><ul><ul><li>Set of programs to access the data </li></ul></ul><ul><ul><li>An environment that is both convenient and efficient to use </li></ul></ul><ul><li>Database Applications: </li></ul><ul><ul><li>Banking: all transactions </li></ul></ul><ul><ul><li>Airlines: reservations, schedules </li></ul></ul><ul><ul><li>Universities: registration, grades </li></ul></ul><ul><ul><li>Sales: customers, products, purchases </li></ul></ul><ul><ul><li>Online retailers: order tracking, customized recommendations </li></ul></ul><ul><ul><li>Manufacturing: production, inventory, orders, supply chain </li></ul></ul><ul><ul><li>Human resources: employee records, salaries, tax deductions </li></ul></ul><ul><li>Databases touch all aspects of our lives </li></ul>
  16. 16. Disadvantages <ul><li>size </li></ul><ul><li>complexity </li></ul><ul><li>cost </li></ul><ul><li>Additional hardware costs </li></ul><ul><li>Higher impact of failure </li></ul><ul><li>Recovery more difficult </li></ul>