netbackup for oracle

Hi,

   As i am beginner ..i have a doubt on backup for oracle.

before going into the actual work..look into the following steps like:-

1. pre-intallation (ie pushing nbu for oracle services in client machine)

2. licensing

3.post installation

4.policy creation

5.script parameters

6. generic code for oracle

Here my question is :- do we need to install the oracle into the master server....as in SQL ...we get license for the Sql , create batch file and save, and then follow the normal procedure of backup on nbuconsole....

So what the difference between two DB Agents.......

Please explain me in a simple words.