There are a number of books on the market which deal with securing Oracle.
Unfortunately, most of these books are like the sorts of survey classes you take as an undergraduate - strong on theory, light on practicality.
I decided to make it real, get rid of the fluff and like Linus Torvalds said "Talk is cheap, show me the code!" (He invented the Linux OS).
I list the things you should do, the reasons you should do these things, and I also provide you with the code to automate as many of these security recommendations as possible.