Just use a connection to your system that uses as login your apps user (check your topology)
I am using "ODI_USER" with other privileges....I just need to execute the one step as "apps"
So make another dataserver with apps as user, model it into Designer (APP_MODEL) and in your step put app_model as model (remember to put oracle as technology).
If your DBA makes some noise he/she can type apps pass in topology.
let me know