Ok,

The role of the DBA is to have the ball rolling. Primary job is to keep the uptime of the databases as nearly as 100%. You would be required for understanding the nature of the business and set up the backup strategy. Create a backup /plan and be sure that you can recover your databases to the point of time required. This also means you do your regular 'Backup Testing' .

The role of the database administrator starts from installing the software/creation of databases, appling patches if required, co-ordinating with the System administrators for various issues (If you re not a SA yourself), monitoring the environment on the regular basis (creating some scripts, or looking for an existing ones), helping the developers with the effective sql's, planning for enhancements, developing different strategies to keep up with the technology and in the company's interest (egs: going for high availability/replications) etc (if you are a consultant...you will dig into it).

Yes, I am an certified DBA.

The Oracle documentation is available online at http://otn.oracle.com
and http://tahiti.oracle.com.
.
Badrinath