Advice on the best way to AUDIT DBA activities in Oracle 12.1 EE on Windows

We are being asked to AUDIT DBA activities to be able to prove DBAs are not DELETING / UPDATING clinical trial data in one of our databases.

The application team cannot tell us which tables to audit so I don't think auding at the object level will work.

I am leaning towards auditing everything that a person with the DBA role does and then we could hopefully filter to find activities against the application schema objects.

I tried the following but it only seems to work if you connect as SYS.

CREATE AUDIT POLICY all_actions_pol ACTIONS ALL;

AUDIT POLICY all_actions_pol by SYS;