OAF : Trace OAF Pages
To enable diagnostic for specific user set Profile Option FND: Diagnostics to YES
See this article about profile option
Now login at application, you will find in global buttons "Diagnostics" link, click it.
Enter the follwing
Diagnostic: Show Log on Screen
Log Level : Statement (1)
Module : %
Now Click go button
Now when opening any page at application you will find trace at button of page.