1. Joel has very useful, detailed article which shows what exactly will be gathered by inventory task for Oracle and other database instance(s).
2. Inventory Solution + Inventory Pack for Servers installed provide ability to get inventory data from Oracle instances
Inventory Pack for Servers required consumes license node(s) per inventoried Server machine
3. In created Gather inventory task, you should open "Advanced" settings and check there db instance type and credentials
4. By default there is some reports to see main data about inventoried Oracle instance(s) on managed computers. But knowing detailed information from Joel article mentioned above, you can always create your custom report