Important Terminologies of DataBase.

1. Transaction Management :

Transaction is a collection of operations that perform a single logical function in a database application. It accesses and possibly updates the data items.
Transaction management ensures the atomicity and durability properties.

2. Database Manager or Storage Manager :

It is a program module which provides the interface between low level data stored in the database and the application programs and queries submitted to the system. Following are responsibilities of database manager :

• Interaction with the file manager : Actual data is stored in the file system. The database manager translates the various DML statements into low level file system commands. This database manager is responsible for actual storing, retrieving and updating of data in the database.

• Integrity enforcement : Consistency constraints are specified by database administrator. But the responsibility of database manager is to enforce, implement or check those constraints.

• Security enforcement : It is the responsibility of database manager to enforce the security requirements.

• Backup and recovery : It is the responsibility of database manager to detect system failures and restore the database to a consistent state.
• Concurrency Control : Interaction among the concurrent users is controlled by database manager.
The storage manager or database manager is thus responsible for :
• Storing the data,
• Retrieving the data and
• Updating of data in the database.

3. Database Administrator :

The person having central control over the system is called database administrator.
• Schema Definition : Database schemas are written by database administrator. These database schemas are translated by DDL complier to a set of tables, that are permanently stored in the data dictionary.
• Storage structure and Access method definition : The DBA creates appropriate storage structures and access methods by writing a set of definitions which is translated by data storage and data definition language compiler.
• Schema and Physical organization modification : DBA writes a set of definitions to modify the database schema or description of physical storage organization.
• Granting of authorization for data access : DBA is responsible for granting the access to the database.
• Integrity-constraint specification : Integrity constraints are written by DBA and they are stored in a special file, which is accessed by database manager, while updating the data.

4. Database Users :

There are four different types of database users :
• Application Programmers : These are computer professionals who interact with the system through DML calls, which are embedded in a program written in a host language. These programs are commonly referred to as application programs.
• Sophisticated Users : They interact with the system through their requests written using a database query language. This request is referred to as a query.
• Specialized Users : They are sophisticated users who write specialized database applications that do not fit into the traditional data processing framework. Examples of specialized database applications are .
(i) Knowledge based,
(ii) Expert system,
(iii) Computer Aided Design System.

5. Naive Users :

They are unsophisticated users who interact with the system by involving one of the permanent application programs that have been written previously.