Congratulations. You have passed the first hurdle to a new position. Though it seems trite, just be yourself in the technical interview. For better or worse, you will not increase your technical knowledge in the next several days, so you will just have to go with what you have.
In the interview, do not oversell nor undersell your abilities. If someone asks a question concerning an area you do not know about, do not bluff, but do prepared to explain how to find the answer. Hint: Talk to some of the other DBA-types at work and ask them where they find answers to problems. You can also look through the Oracle web-site, but do not use this as an easy way out - talk to the other DBAs.
Do not be apologetic about lack of information. You have not done this job before, so do not be embarrassed about not knowing how to do it. As an interviewer, I would prefer someone knows an answer, but I also like then to show initiative by knowing how to find answers. If someone spends time explaining why he does not know the answer, it raises a concern with me as to how he will respond when confronted with a new problem. Show your "can do" side when answering your questions.
Lastly, ask for a debrief at the end of the interview. Bluntly ask whether what strengths and weaknesses the interviewer sees. If you do not get the position (remember most positions have more than one applicant), you can improve yourself before the next opportunity. If you get the position, you know areas to work on to improve your performance in the position.
By progressing to the technical interview, your company has shown confidence in you. Go into the interview and do your best, but place the interview in perspective. Regardless of the outcome, you will come out of the interview stronger than when you went in. You have passed the first step to acquiring a new position. Good luck in the technical interview.
Wayne
