Recently I am testing and verifying the problems&questions regarding migrating to "oracle" user on Oracle 12c.
We have an SAP note "1888485 - Database Parameter for 126.96.36.199" which tells us the right database parameters should be set. Please verify those "Database Parameter Settings for Specific Platforms" database parameters carefully.
use_large_pages is the one that adjusted for oracle owner, after migrating "oracle" user, you have to adjust it from OS level as well according to SAP note 1672954.
We have met a very bad performance issue after upgrading to oracle 12c, it took us days to dig the cause in wrong way. We were getting deeper and deeper into wrong road for days (reviewing sqls, io, etc. :???: ). Luckily we finally found this parameter use_large_pages needs to adjusted for oracle user. Keeping parameters right is the prerequisite for tuning database performance.