Introduction

Thank you for purchasing this book. We worked hard on it for a long time. Our hope is that you find it useful as you begin to work with Exadata. We've tried to introduce the topics in a methodical manner and move from generalizations to specific technical details. While some of the material paints a very broad picture of how Exadata works, some is very technical in nature, and you may find that having access to an Exadata system where you can try some of the techniques presented will make it easier to understand. Note that we've used many undocumented parameters and features to demonstrate how various pieces of the software work. Do not take this as a recommended approach for managing a production system. Remember that we have had access to a system that we could tear apart with little worry about the consequences that resulted from our actions. This gave us a huge advantage in our investigations into how Exadata works. In addition to this privileged access, we were provided a great deal of support from people both inside and outside of Oracle for which we are extremely grateful.

The Intended Audience

This book is intended for experienced Oracle people. We do not attempt to explain how Oracle works except as it relates to the Exadata platform. This means that we have made some assumptions about the reader's knowledge. We do not assume that you are an expert at performance tuning on Oracle, but we do expect that you are proficient with SQL and have a good understanding of basic Oracle architecture.

How We Came to Write This Book

In the spring of 2010, Enkitec bought an Exadata V2 Quarter Rack. We put it in the tiny computer room at our office in Dallas. We don't have a raised floor or anything very fancy, but the room does have its own air conditioning system. It was actually more difficult than you might think to get Oracle to let us purchase one. They had many customers that wanted them, and they were understandably protective of their new baby. We didn't have a top-notch data center to put it in, and even the power requirements had to be dealt with before they would deliver one to us. At any rate, shortly after we took delivery, through a series of conversations with Jonathan Gennick, Randy and I agreed to write this book for Apress. There was not a whole lot of documentation available at that time, and so we found ourselves pestering anyone we could find who knew anything about it. Kevin Closson and Dan Norris were both gracious enough to answer many of our questions at the Hotsos Symposium in the spring of 2010. Kevin contacted me some time later and offered to be the official technical reviewer. So Randy and I struggled through the summer and early fall attempting to learn everything could.

I ran into Tanel at Oracle Open World in September, 2010, and we talked about a client using Exadata that he had done some migration work for. One thing led to another, and eventually he agreed to join the team as a co-author. At Open World, Oracle announced the availability of the new X2 models, so we had barely gotten started and we were already behind on the technology.

In January of 2011, the X2 platform was beginning to show up at customer sites. Enkitec again decided to invest in the technology, and we became the proud parents of an X2-2 quarter rack. Actually, we decided to upgrade our existing V2 quarter rack to a half rack with X2 components. This seemed like a good way to learn about doing upgrades and to see if there would be any problems mixing components from the two versions (there weren't). This brings me to an important point.

A Moving Target

Like most new software, Exadata has evolved rapidly since its introduction in late 2009. The changes have included significant new functionality. In fact, one of the most difficult parts of this project has been keeping up with the changes. Several chapters underwent multiple revisions because of changes in behavior introduced while we were writing the material. The last version we have attempted to cover in this book is database version 11.2.0.2 with bundle patch 6 and cellsrv version 11.2.2.3.2. Note that there have been many patches over the last two years and that there are many possible combinations of database version, patch level, and cellsrv versions. So if you are observing some different behavior than we have documented, this is a potential cause. Nevertheless, we welcome your feedback and will be happy to address any inconsistencies that you find. In fact, this book has been available as part of Apress's Alpha program, which allows readers to download early drafts of the material. Participants in this program have provided quite a bit of feedback during the writing and editing process. We are very thankful for that feedback and somewhat surprised at the detailed information many of you provided.

Thanks to the Unofficial Editors

We have had a great deal of support from a number of people on this project. Having our official technical reviewer actually writing bits that were destined to end up in the book was a little weird. In such a case, who reviews the reviewer's writing? Fortunately, Arup Nanda volunteered early in the project to be an unofficial editor. So in addition to the authors reviewing each other's stuff, and Kevin reviewing our chapters, Arup read and commented on everything, including Kevin's comments. In addition, many of the Oak Table Network members gave us feedback on various chapters throughout the process. Most notably, Frits Hoogland and Peter Bach provided valuable input.

When the book was added to Apress's Alpha Program, we gained a whole new set of reviewers. Several people gave us feedback based on the early versions of chapters that were published in this format. Thanks to all of you who asked us questions and helped us clarify our thoughts on specific issues. In particular, Tyler Muth at Oracle took a very active interest in the project and provided us with very detailed feedback. He was also instrumental in helping to connect us with other resources inside Oracle, such as Sue Lee, who provided a very detailed review of the Resource Management chapter.

Finally I'd like to thank the technical team at Enkitec. There were many who helped us keep on track and helped pick up the slack while Randy and I were working on this project (instead of doing our real jobs). The list of people who helped is pretty long, so I won't call everyone by name. If you work at Enkitec and you have been involved with the Exadata work over the last couple of years, you have contributed to this book. I would like to specifically thank Tim Fox, who generated a lot of the graphics for us in spite of the fact that he had numerous other irons in the fire, including his own book project. We also owe Andy Colvin a very special thanks as a major contributor to the project. He was instrumental in several capacities. First, he was primarily responsible for maintaining our test environment, including upgrading and patching the platform so that we could test the newest features and changes as they became available. Second, he helped us hold down the fort with our customers who were implementing Exadata while Randy and I were busy writing. Third, he was instrumental in helping us figure out how various features worked, particularly with regard to installation, configuration, and connections to external systems. It would have been difficult to complete the project without him.

Who Wrote That?

There are three authors of this book, four if you count Kevin. It was really a collaborative effort among the four of us. But in order to divide the work we each agreed to do a number of chapters. Initially Randy and I started the project and Tanel joined a little later (so he got a lighter load in terms of the assignments, but was a very valuable part of team, helping with research on areas that were not specifically assigned to him). So here's how the assignments worked out:

Kerry: Chapters 1–6, 10, 16.

Randy: Chapters 7–9, 14–15, and about half of 13

Tanel: Chapters 11–12, and about half of 13

Kevin: Easily identifiable in the “Kevin Says” sections

Online Resources

We used a number of scripts in this book. When they were short or we felt the scripts themselves were of interest, we included their contents in the text. When they were long or just not very interesting, we sometimes left the contents of the scripts out of the text. You can find the source code for all of the scripts we used in the book online at www.ExpertOracleExadata.com. Appendix C also contains a listing of all the diagnostic scripts along with a brief description of their purpose.

A Note on “Kevin Says”

Kevin Closson served as our primary technical reviewer for the book. Kevin was the chief performance architect at Oracle for the SAGE project, which eventually turned into Exadata, so he is extremely knowledgeable not only about how it works, but also about how it should work and why. His duties as technical reviewer were to review what we wrote and verify it for correctness. The general workflow consisted of one of the authors submitting a first draft of a chapter and then Kevin would review it and mark it up with comments. As we started working together, we realized that it might be a good idea to actually include some of Kevin's comments in the book, which provides you with a somewhat unique look into the process. Kevin has a unique way of saying a lot in very few words. Over the course of the project I found myself going back to short comments or emails multiple times, and often found them more meaningful after I was more familiar with the topic. So I would recommend that you do the same. Read his comments as you're going through a chapter, but try to come back and reread his comments after finishing the chapter; I think you'll find that you will get more out of them on the second pass.

How We Tested

When we began the project, the current release of the database was 11.2.0.1. So several of the chapters were initially tested with that version of the database and various patch levels on the storage cells. When 11.2.0.2 became available, we went back and retested. Where there were significant differences we tried to point that out, but there are some sections that were not written until after 11.2.0.2 was available. So on those topics we may not have mentioned differences with 11.2.0.1 behavior. We used a combination of V2 and X2 hardware components for our testing. There was basically no difference other than the X2 being faster.

Schemas and Tables

You will see a couple of database tables used in several examples throughout the book. Tanel used a table called T that looks like this:

I used several variations on a table called SKEW. The one I used most often is SKEW3, and it looked like this:

This detailed information should not be necessary for understanding any of our examples, but if you have any questions about the tables, they are here for your reference. Also be aware that we used other tables as well, but these are the ones we used most often.

Good Luck

We have had a blast discovering how Exadata works. I hope you enjoy your explorations as much as we have, and I hope this book provides a platform from which you can build your own body of knowledge. I feel like we are just beginning to scratch the surface of the possibilities that have been opened up by Exadata. Good luck with your investigations and please feel free to ask us questions and share your discoveries with us at www.ExpertOracleExadata.com.