I've not done that specific exam. I did these to get my PL/SQL OCP:
I can only talk about my experience of these exams.
In many cases the questions can be answered without looking at the exhibits. Read the whole question and understand what it is asking for before looking at the exhibits. That way if you have to look at the exhibit, you are looking at something specific, not just reading through all the code. Like when you are debugging code. You don;t start ar line 1 and read through, you jump straight to the areas of code that are relevant to the bug.
For example, if a question said something about a runtime error error on an assignment, you would only look at lines where values are assigned to variables, like ":=" and "SELECT ... INTO".
If you have not read the whole question and start examining the exhibit, you don;t know what you are looking for, so it could take you ages to find something odd.
Also, in all but 2 cases I can remember, schema diagrams have been all but useless in answering the questions. Don't study them before reading the question.
So in conclusion:
1) Read the whole question and attempt to answer it without referencing the exhibits.
2) Use the exhibits to confirm your anwer, or to help find the answer if it is not obvious from point 1.
When I use this method I can usually get through the exams in about 30 mins. Remember though, I'm an native English speaker and I've been doing this stuff for 15+ years, so don't expect it to be so easy if English is your second language, or if you have less experience.