Thursday, 29 January 2015

Functions of Database Administrators


Functions of Database Administrator / List the major functions of a DBA / What are the functions of a database administrator? / Functions of DBA with simple examples


Functions of Database Administrator (DBA)

Database Administrator is one of the stakeholders of DBMS. He is role is to control the database system as a whole. The major functions of a DBA are the following;

  • Selection of hardware and software: for example, he has to anticipate the size of the database in the near future and go for necessary hardware.
  • Schema definition / Database structure definition: DBA is the person who defines the structure of a database and creates databases using set of DDL statements. For example, DBA can create a table using SQL as follows;
CREATE TABLE stu(Regno CHAR(5) PRIMARY KYE, SName VARCHAR(30) NOT NULL, Phone NUMBER(10) NOT NULL);

  • Storage structure and access-method definition: DBA defines the way to store data and the ways to access the stored data. Some of the access methods include, how to use indexes?, when to use indexes? how to store tables? etc.
  • Schema and physical organization modification: DBA changes the structure of the tables or other database components, modifies the physical organization of data files etc. This alteration is mainly performed to improve the system efficiency. For example, the structure of the table stu created above can be modified as follows to add another attribute Gender;
ALTER TABLE stu ADD Gender CHAR(1) NOT NULL CHECK (Gender in (‘M’, ‘F’));

  • Granting of authorization for data access: DBA decides and permits various users to access database. Normally, one cannot permit all the users to access all the content of a database. In reality, except DBA all the other users are considered as restricted users. DBA can restrict users to access only a portion of a table, only to view records, only to insert records, only to insert and modify records and so on. For example, the following statement permits the user Ram to view the records from the table stu;
GRANT SELECT ON stu TO Ram;

  • Routine maintenance: Schema definition, alteration, and physical organization modification are usually done only very few times by the DBA. The major work is to maintain the database and its users. The following list shows some of the routine maintenance work of a DBA;

Authorizing users
Backing up of database
Recovery of database in case of failures
Checking the availability of disk space
Checking the performance of the DBMS
Monitoring for unauthorized access etc.
 

All the functions listed above are well defined and includes various sub-functions according to the business application.


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