Oracle Press has some nice study guides to help you prepare for the Oracle 9i OCP exams. I use the books from Oracle Press to study for my OCP exams. In fact, I have the 10g Upgrade Exam book on my nightstand right now as I am preparing to take that exam in the very near future.
There is a boxed set of four books for all four exams for the Oracle 9i OCP DBA certification. You can see this boxed set here.
You are under no obligation to purchase these from Amazon. I just used a link to their Web site to show you the material. You can purchase these products from other sources too.
This was first published in May 2006