A database administrator's responsibilities can include the following tasks: 

Installing and upgrading the Oracle server and application tools 

Allocating system storage and planning future storage requirements for the database system 

Creating primary database storage structures (tablespaces) after application developers have designed an application 

Creating primary objects (tables, views, indexes) once application developers have designed an application 

Modifying the database structure, as necessary, from information given by application developers 

Enrolling users and maintaining system security 

Ensuring compliance with your Oracle license agreement 

Controlling and monitoring user access to the database 

Monitoring and optimizing the performance of the database 

Planning for backup and recovery of database information 

Maintaining archived data on tape 

Backing up and restoring the database 

Contacting Oracle Corporation for technical support