Function and Services of Database Management System (DBMS)
Database
Management System
“A Database Management System (DBMS) is defined as software
that provides an environment that as
software that provides an environment
that is both convenient and efficient to use in storing and retrieving the data
of an enterprise .”
In short, A Database Management System means a system
managing the database of a particular enterprise in both the convenient and
efficient manner.
Database Management System (DBMS) Functions and Services
§ DBMS performs several important functions that guarantee the integrity and consistency bof the data in the database.
§ Those functions transparent to end users and can be accessed only through the use of DBMS.
A DBMS performs several important functions that guarantee
integrity and consistency of data in the database.
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1. Data storage Management:-
The DBMS creates the complex Structures required for data storage
in the physical database. It provides a mechanism for management of permanent storage
of the data.
2. Transaction Management:-
A transaction is a series of database operations, carried
out by an application program, which access or changes the contents of the
database. Therefore, a DBMS must provide a mechanism to ensure either that all
the updates corresponding to a given transaction are made or that none of them
is made.
3. Integrity
Services:-
Database integrity refers to the correctness and consistency
of stored data and is specially important in transaction oriented database
system. Therefore, a DBMS must provide to ensure that both the data in the
database and changes to the data follow certain rules. This minimises data
redundancy and maximizes data consistency. The data relationship stored in the
data dictionary are used to enforce data integrity. Various types of integrity
mechanisms and constrains may be supported to help ensure that the data values
within the database are valid, that the operations performed on those values
are valid and that the database remains in a consistent state.
4. Backup and
Recovery Management:-
The DBMS provides mechanisms for different types of
failures. This prevents the loss of data. The recovery mechanisms of DBMS, make
sure that the database is returned to a consistent state after a transaction
fails or aborts due to a system crash, media failure, hardware or software
errors, power failure, and soon.
5. Concurrency
Control Services:-
Since DBMS support sharing of data among multiple uses, they
must provide a mechanism for managing for concurrent access to the database.
DBMS’s ensure that the database is kept in consistent state and that the
integrity of the data is preserved. It ensures that the database is Updated
Correctly when multiple users are updating the database concurrently.
6. Data Manipulation
management:-
DBMS furnishes users with the ability to retrieve, update
and delete existing data in the data in the database or to add new data to the
database. It includes DML processor component to deal with the data
manipulation language (DML).
7. Data Dictionary /
System Catalog Management:-
The DBMS provides a data dictionary or system catalog
function in which descriptions of data items are stored and which is accessible
to users. System catalog or data dictionary is a system database, which is a
repository of information of describing the data in the database. It is the
data about the data or metadata. For example, the DBMS will consult the system
catalog to verify that a requested table exists and the users issuing the
request has the necessary access privileges.
8. Authorization /
Security Management:-
The DBMS protects the database against unauthorized access,
either intentional or accidental. It furnishes mechanism to ensure that only
authorized users can access the database. It creates a security system that
enforces user's security and data privacy within the database. Security rules
determine which users can access the database, which data items each users may
access and which data operations (add, delete, and modify) the user may
perform.
9. Utility
Services:-
The DBMS provides a set of utility services used by the DBA
and the database designer to create, implement, monitor and maintain the
database. These utility services help to DBA administer the database
effectively.
10. Database Access
and Application Programming Interfaces:-
All DBMSs provides interface to enable applications to use
DBMS Services. They provide data access via structured query language (SQL).
The DBMS query language contains two components:
- A data definition language (DDL)
- A manipulation Language (DML)
DDL defines the structure in which the data are stored and
the DML allows end user to extract the data from the database.
The DBMS also
provides data access to application programmers via procedural languages such
as C, C++, Java and others.
11. Data Independent
Services:-
The DBMS must support the independence of programs from the
actual structure of the database.
12. Data Definition
Services:-
The DBMS accepts the data definitions such as external
schema, the conceptual schema, the internal schema, and all the associated
mapping in source form. It converts them to the appropriate object from using a
DDL processor component for each of various data definition languages (DDLs).