For written test, read PAC previous year papers.
PAC conducts written on behalf of oracle. And most of the questions are repeated every year. In my campus, oracle hired for its 4 units (fusion applications, people soft, mysql, oracle financial services).
I don't know if oracle server technologies use same paper or different one.

my interview was a little strange.
In first round of tech interview, interviewer just asked apti questions. It sound bizarre, but it is what actually happened. Questions were like:
if a pipe fills a cistern in 37.5 mins and other fills it in 40 mins, after how many mins should we stop inflow of pipe 1 to make sure that cistern fills in 30 mins. (exact timing may vary, i dont remember them exactly)

2) at what time between 3 and 4, minute and hour hand align exactly over each other and at what time do the align at 180 degrees to each other?
3) 3 switch and a bulb in the room. which swich operates the bulb
4) a orange seller sells half more than half of the total oranges she has on each day. All her oranges are sold on 3rd day. Find how many oranges she initially had.
(ans is 7)
tech interview 2
1)general questions like what is polymorphism, inheritance, containership
2)what is heap memory, stack memory
3)A puzzle: if we have 25 horses and we can use only 5 horses in one race, in how many races can we get fastest 3 horses. ( ans is 7)

Questions about my project which i mentioned in resume
why do i want to join oracle?
have i been to banglore ever?
what challenge do you expect to face if you move out of your hometown?

1) be +ve that you can crack it.
2)find previous year written test papers for each company you decide to appear. They are immensely helpful in clearing written

around 300 applied, there was no major shortlisting in written. Many got through.
finally 9 were selected. I got selected in peoplesoft group of oracle.
I think it was positive attitude that favored me the most. Rest luck also favored me. No DS questions were asked from me while other candidates faced tough trees and other DS questions. Communications skills also played a role. A couple of my friends got rejected in HR