With old FME versions, it was possible to use both lowercase and uppercase attributes when writing out to Oracle databases.This is no longer possible since FME 2014 build 14131.
The only workaround I found is to copy+paste feature types from old workspaces to new ones. It is not really user friendly and I assume that in this manner the old 2014 Oracle writer is used even with FME 2016.

