I have already passed 4 of the 5 exams , Administration is definetly the hardest because it covers many many points compared to any other exam.

But after all there is no easy exam here , Oracle is ranked is the most hard exams after Cisco and it is the most valued certification concerning software ( Cisco mainly concentrate on hardware and networking ) ,, it is all about study and it is very common to pass the exam with one or 2 questions over the needed limit.

Wishing you all the best