Database Administrator
One of the main perpose for having the database management system is to have control of both data or programs accessing that data. The person having like control over the system is called as the database administrator (DBA). The DBA administers the 3 stages of the database and tells the global view or conceptual level of the database. The DBA also displays the external view of the applications and several users and is responsible for the definition and execution of the internal level, as well as the storage structure and access techniques to be used for the optimum performance of the DBMS. A modification to any of the 3 levels due to varies in the organisation and/or emerging technology is under the control of the DBA.
Mappings among the internal and the conceptual levels, as well as between the conceptual and external levels, are also describe through the DBA. The DBA is responsible for granting permission to the users of the database and remainsthe profile of each user in the database. This profile defines the permissible activities of a user on that portion of the database accessible to the user through one or more user views. The user profile could be used by the database system to confirm in which a particular user can present a given operation on the database.
The DBA is also responsible for describing procedures to recover the database from natural, failures due to human, or hardware causes along with minimal loss of data. This recovery procedure should permit the organisation to continue to function and the intact portion of the database has to continue to be available.
Therefore, the functions of DBA are:
- Schema definition: Formation of the original database schema is accomplished through writing a set of definitions which are translated through the DDL compiler to a set of tables that are always stored in the data dictionary.
- Storage Structure and access method definition: The Formation of appropriate storage structure and access techniques is accomplished through writing a set of definitions which are translated by the definition language compiler and data storage.
- Schema and Physical organisation modification: DBA includes either the changes of the database schema or the description of the physical storage organisation. These changes, though relatively rare, are accomplished by writing a set of definitions which are used through either the data storage or the DDL compiler and definition language compiler to make modification to the appropriate internal system tables (for example the data dictionary).
- Granting of authorisation for data access: DBA allows the granting of different types of authorisation for data access to the various users of the database.
- Integrity constraint specification: The DBA shows the constraints. These constraints are put in a special system structure, the data dictionary which is consulted through the database manager prior to any data manipulation. Data Dictionary is one of the precious tools in which the DBA uses to carry out data administration.