I am finally getting around to finishing my four-part blog series on people who have had the most influence on my Oracle performance tuning work. The previous three people were Craig Shallahamer, Don Burleson, and Cary Millsap. The last person is Jonathan Lewis. These four people, listed and blogged about in chronological order, had the most influence on my understanding of how to do Oracle database performance tuning. There are many other great people out there and I am sure that other DBAs would produce their own, different, list of people who influenced them. But this list reflects my journey through my Oracle database career and the issues that I ran into and the experiences that I had. I ran into Jonathan Lewis’ work only after years of struggling with query tuning and getting advice from others. I ran into his material right around the time that I was beginning to learn about how the Oracle optimizer worked and some of its limits. Jonathan was a critical next step in my understanding of how Oracle’s optimizer worked and why it sometimes failed to pick the most efficient way to run a query.
Jonathan has produced many helpful tuning resources including his blog, his participation in online forums, and his talks at user group conferences, but the first and most profound way he taught me about Oracle performance tuning was through his query tuning book Cost-Based Oracle Fundamentals. It’s $30 on Amazon and that is an incredibly small amount of money to pay compared to the value of the material inside the book. I had spent many hours over several years trying to understand why the Oracle optimizer some times choses the wrong way to run a query. In many cases the fast way to run something was clear to me and the optimizer’s choices left me stumped. The book helped me better understand how the Oracle optimizer chooses what it thinks is the best execution plan. Jonathan’s book describes the different parts of a plan – join types, access methods, etc. – and how the optimizer assigns a cost to the different pieces of a plan. The optimizer chooses the plan with the least cost, but if some mistake causes the optimizer to calculate an unrealistic cost then it might choose a poor plan. Understanding why the optimizer would choose a slow plan helped me understand how to resolve performance issues or prevent them from happening, a very valuable skill.
There is a lot more I could say about what I got from Jonathan Lewis’ book including just observing how he operated. Jonathan filled his book with examples which show concepts that he was teaching. I think that I have emulated the kind of building of test scripts that you see throughout his book and on his blog and community forums. I think I have emulated not only Jonathan’s approach but the approaches of all four of the people who I have spotlighted in this series. Each have provided me with profoundly helpful technical information that has helped me in my career. But they have also provided me with a pattern of what an Oracle performance tuning practitioner looks like. What kind of things do they do? To this point in my career I have found the Oracle performance tuning part of my job to be the most challenging and interesting and probably the most valuable to my employers. Jonathan Lewis and the three others in this four-part series have been instrumental in propelling me along this path and I am very appreciative.