Expert

Jonathan Lewis's picture

I was sent the following email a few years ago. It’s a question that comes up fairly frequently and there’s no good answer to it but, unusually, I made an attempt to produce a response; and I’ve decided that I’d start this year by presenting the question and quoting the answer I gave so here, with no editing is the question:

I’m disturbing you for some help about becoming an Oracle master expert. Probably you are getting this kind of emails a lot but I would be appreciate if you give a small answer to me at least.

First, shortly I want to introduce my self. I’m an *Oracle Trainer* in Turkey Oracle University for 2 years. Almost for 4 years, I worked as software engineer and meet with Oracle on these days. After a while I decided to develop myself in Oracle database technologies and become trainer as i said. I also give consultancy services about SQL / PLSQL development and especially* SQL / PLSQL tuning*. I really dedicate myself to these subjects. As a trainer I also give DBA workshop lectures but in fact I didnt actually did dba job in a production system. I have the concept and even read everything I found about it but always feel inadequate because didnt worked as a DBA on a production system. So many DBA’s has taken my class and they were really satisfied (they have got all answers for their questions) but I did not. I’m a good trainger (with more that 97 average points in oracle evaluations) but I want to be best.

Even in SQL / PLSQL tuning, I know that I am really good at it but I also aware that there are some levels and I can not pass through the next level. for ex: I can examine execution plan (index structures, access paths etc), find cpu and io consumption using hierarchical profiler and solve the problem but can’t understand yet how to understand how much IO consumed by query and understand slow segments. if you remember, for a few days ago, on OTN you answered a question that I involved about sequence caching and Log file sync event. There, I said that sequence can cause to log file sync event (and as you said that was true) but when someone else write a simple code and couldnt see this event, I couldnt answer to him, you did (you said that it was because optimizing).

that is the level what i want to be. I am really working on this and age on 29. but whatever I do I cant get higher. I need a guideness about that. I even worked free for a while (extra times after my job here). I need your guideness, as I said I can work with you if you want to test and I want to learn more advanced topics while working. In Turkey, I couldn’t find people who can answer my questions so I can not ask for guideness to them.

And my (impromptu, and unedited) reply:

Thank you for your email. You are correct, I do get a lot of email like this, and most of it gets a stock response; but yours was one of the most intelligently written so I’ve decided to spend a little time giving you a personal answer.

Even if you were to spend a few years as a DBA, you would probably not become the sort of expert you want to be. Most DBAs end up dealing with databases that, for want of a better word, we could call “boring”; for a database to be interesting and show you the sorts of problems where you have to be able to answer the types of question I regularly answer you probably need to be the DBA for a large banking or telecoms system – preferably one that hasn’t been designed very well – that has to handle a very large volume of data very quickly. On these extreme systems you might find that you keep running into boundary conditions in Oracle that force you to investigate problems in great detail and learn all sorts of strange things very quickly. On most other systems you might run into a strange problem very occasionally and spend several years on the job without once being forced to solve any difficult problems very quickly.

If you want to become an expert, you need to be a consultant so you get to see a lot of problems on lots of different systems in a very short time; but you can’t really become a consultant until you’re an expert. As a substitute, then, you need to take advantage of the problems that people report on the OTN database forum – but that doesn’t mean just answering questions on OTN. Look for the problems which people have described reasonably well that make you think “why would that happen”, then try to build a model of the problem that has been described and look very closely at all the statistics and wait events that change as you modify the model. Creating models, and experimenting with models, is how you learn more.

Take, for example, the business of the sequences and pl/sql – you might run the test as supplied with SQL_trace enabled to see what that showed you, you could look very carefully at the session stats for the test and note the number of redo entries, user commits, and transactions reported; you could look at the statistics of enqueue gets and enqueue releases, ultimately you might dump the redo log file to see what’s going into it. Many of the tiny little details I casually report come from one or two days of intense effort studying an unexpected phenomenon.  (The log file sync one was the result of such a study about 15 years ago.)

 Happen new year to all my readers.

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