Grade Change Audit is done through table triggers.
There's a bit
of info on this Customer Connection article: https://support.oracle.com/epmos/faces/DocContentDisplay?id=1495960.1
To turn on Grade Auditing, a SQL script just needs to be run
against environment.
The grade audit one is called ssr_mss_grade_tr.sql.
You'll also
see a bunch of other scripts in there starting with ssr_ to audit other tables.
If any future auditing is
needed, just run the appropriate script in that folder. Only run scripts that
contain _mss_ (Microsoft SQL Server); the other scripts are for Oracle and DB2.