This Preface and the entire book are a little bit different—and that is by design. Both authors wrote this book understanding that our target audience often does not have time to read a whole book, or the Oracle documentation, from cover to cover. As such, we wrote this book with the idea that the table of contents and headings should tell you exactly what is being covered. Bullet lists will be used to quickly highlight key points where appropriate. Where concepts need to be explained in more detail, a supporting narrative is supplied. Another difference is that we make multiple references to Oracle documentation rather than attempting to rewrite everything. This is also by design. Having seen Oracle documentation evolve over the years, both authors, and our publisher, recognize the intrinsic value of getting specific detailed information straight from the "horse's mouth". To promote the development of overall expertise, we focus on helping our readers effectively use all the tools available. The Oracle documentation is one of your most valuable tools. At times, Oracle documentation can be difficult to follow or find information within, but once you develop an expertise in using the documentation, the expertise in the functionality is not far behind. The focus of this book is not to replace the Oracle documentation, but rather to be a quick reference companion to the Oracle documentation.