Monday, April 25, 2011

DBMS Database management system


DBMS Database management system

The DBMS (Database management system) is usually a commercial product whose purpose is to create, process, and administer the database.

DBMS tasks include:
  • create database sructure;
  • create table structures;
  • create suporting sructures;
  • data retrieval;
  • data update;
  • maintain database structures;
  • ensure data integrity;
  • control concurrency/ handle shared update;
  • ensure security;
  • backup/ recovery;
  • replication support;
  • catalogue/ data dictionary (metadata).
Advantages of a DBMS:
  • A DBMS makes it easy to search through the data (queries). In a spreadsheet, you can’t easily access related data; you have to search manually for it;
  • A DBMS controls redundancy (it doesn’t necessarily eliminate it,) which in turn
    • saves storage space;
    • makes updates easy – less processing time;
    • reduces inconsistent data.
A spreadsheet has redundancy which wastes storage space, takes more processing time and creates inconsistent data.
  • A DBMS has security features. A spreadsheet does not;
  • A DBMS can create customized forms to view, enter and edit data. A spreadsheet cannot;
  • A DBMS can create customized reports to get professional hardcopy output. A spreadsheet cannot;
  • A DBMS makes it easy to maintain data integrity because there are mechanisms that will ensure that the data satisfy all established rules (aka integrity constraints). A spreadsheet cannot do this;
  • A DBMS is more flexible in using the data for new purposes. A spreadsheet isn’t;
  • A DBMS makes sharing data easy because it is stored in just one location;
  • A DBMS can provide controlled access to the data, forms, reports and other objects through a switchboard (which is actually just another form);
  • A DBMS can balance conflicting requirements. (DBA structures data to benefit the whole organization. An individual (or group) may be less well served, but whole is better off);
  • A DBMS increases productivity because programmers are freed up for other tasks. Also, users can do things they couldn’t do before unless they had programmers;
  • A DBMS provides for data independence – the structure of the data is independent of the programs that process the data. So the structure can be changed without the programs having to change.
Disadvantages of a DBMS
  • Large size – occupies lots of hard disk space and RAM;
  • Complexity – hard to learn, wrong choices may spell irreversible disaster later;
  • Greater impact of failure – failure impacts all users;
  • More difficult recovery – since it is more complex.



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