DBMS Overview and Definitions | Database Management System

DBMS Overview and Definitions | Database Management System

DBMS Overview and Definitions : A database is a Collection of related information/data and a DBMS is a software system that helps to manage such database. DBMS provides a superior system of data handling than flat file approach, leading to high level of flexibility, consistency and simplicity. They are generalized file processing Systems for manipulating database.

Some popular DBMS are: Oracle, MS, DBZ, MS SQL, ingeres, MY SQL.

A DBMS is collection of Software modules that along with the support of hardware provides excellent data management facilities which are not available in other above discussed method of database management.

A database management system (DBMS) is a software system that enables users to define, create, and maintain the database and provides Controlled access to this database through the application program. A DBMS uses Data Definition Language (DDL) and Data Manipulation Language (DML) in the DBMS.

A DBMS is used to set and monitor a database and helps in inserting, updating and retrieval of data from that database. In general most DBMS provides following facilities:

  1. Creation of data files/tables (Schema definition)
  2. Deletion of data files
  3. Modification in the structure of data files (alteration in table structure)
  4. insertion of data
  5. Updation of data
  6. Deletion of data
  7. Retrieval of data collectively or selectively
  8. Enforcement of constraints on data values
  9. Security of data access
  10. Generation of reports
  11. Mathematical functions on data stored in the database
  12. Maintenance of data integrity
  13. Controlled access

Such facilities and many more features are available in all modern DBMS Such as Oracle of Oracle corporation, MS SOL of Microsoft, My SOLa free compact DBMS, DB2 of IBM etc.

Functions of a DBMS

The functions performed by a typical DBMS are the following:

Data Definition

The DBMS provides functions to define the structure of the data in the application. These include defining and modifying the record structure, the type and size of fields and the various constraints/conditions to be satisfied by the data in each field.

Data Manipulation

Once the data structure is defined, data needs to be inserted, modified or deleted. The functions which perform these operations are also part of the DBMS. These function can handle planned and unplanned data manipulation needs. Planned queries are those which form part of the application. Unplanned queries are ad-hoc queries which are performed on a need basis.

Introduction to DBMS

Data Security & Integrity

The DBMS contains functions which handle the security and integrity of data in the application. These can be easily invoked by the application and hence the application programmer need not code these functions in his/her programs.

Data Recovery & Concurrency

Recovery of data after a system failure and concurrent access of records by multiple users are also handled by the DBMS.

Data Dictionary Maintenance

Maintaining the Data Dictionary which contains the data definition of the application is also one of the functions of a DBMS,

Performance

Optimizing the performance of the queries is one of the important functions of a DBMS. Hence the DBMS has a set of programs forming the Query Optimizer which evaluates the different implementations of a query and chooses the best among them. Thus the DBMS provides an environment that is both convenient and efficient to use when there is a large volume of data and many transactions to be processed.

Technically a DBMS must support following functions:

  1. Data storage, retrieval, and update.
  2. User-accessible catalog.- a DBMS must store information about data in a system catalog and user can access meta-data.
  3. Transaction support-it means that data should be consistent, that is, ensure that either all the updates Corresponding to a given transaction are made or that none of them are made.
  4. Concurrency control-a DBMS is made for several users simultaneously. The DBMS must manage that the users can access data without interfering with another users even though the same data are needed.
  5. Recovery services – a DBMS must have some preparation for different kinds of damages (hard disk or Software damages).
  6. Authorization Services-a DBMS must have control that data is accessed by only authorized users.
  7. Support for data communication – a DBMS must integrate with communication software.
  8. Integrity services – a DBMS must ensure that both the data in the database and changes to the data follow certain rules. There are some rules for consistency of Stored data.
  9. Services to promote data independence-a DBMS must facilitate to support the independence of program from the actual structure of the database. See the beginning of this section “program-data independence”.
  10. Utility services – a DBMS should be provide a set of utility services such as statistical analysis programs, monitoring facilities import facilities, garbage Collection and reallocation.