Well I had the Oracle class and used the Oracle books that they give you in the class, so that helped me in the first exam, I haven't taken the others yet, as I only had the Fundamentals 1 class for Administration and Architecture.
I also have Thomas Kytes One on One expert book. However I think this book is more of a developer tyoe book, so it can give me some insights but not everything in that DBA area.
I still recommend Tom's book to everyone.
Other than that I have self-test software that I bought to practice with.
Good luck.
Also in one of your other three posts I included the link to change your name to be in accordance with JavaRanch's naming policy. Please go there and change your last name in your profile to your correct last name. Thanks
alot Mark