1.3 Functions of 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.

• 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.