Today is Hotsos Symposium 2008 Training Day — one full day with Tom Kyte. I haven’t registered for it so I took the chance to sleep until 10 this morning which was excellent idea considering that last night we were quite late going to bed thanks in parts to the joined demo that James Morle and Mike Erwin organized at the last presentation yesterday. I was in the James’ session and he was demonstrating how to hide latency problem with batching. I suspect that Mike, in the next hall, was showing the impact of MTU settings on cluster interconnect. The end result is that beer bottles travelled between the presentation halls and James ended up with about 3 packs of Guinness and Shiner Bock. That what kept us up longer last night.

James’ presentation itself was excellent — he explained that all performance problems can be caused by either skew or latency. You can’t normally fix skew issue so you just need to be aware and account for it. Latency can sometimes be shortened but usually insignificantly or it’s impractical (i. e. very expensive). It’s also very important to distinguish bandwidth and latency. I like his idea that the efficient way to solve latency is hiding it and there are generally two ways to do that — batching and threading. Improving bandwidth often doesn’t cause any performance improvement without taking latency into account. Very insightful talk. Thanks James.
(more…)

The symposia is still ongoing and my head is slowly filling up — relieved from my presentation, finally, I’m able to focus on others’ sessions.

Yesterday, Tanel Poder presented his new tool Sesspack and his integration with Excel. 3 years ago, I created a similar tool and collected session waits and statistics transformed into differences per the interval and organized in the star schema to simplify the analysis. I tried to write a front-end in PHP — it was taking ages and I didn’t have time. Then I tried APEX (HTMLDB 1.6 back then) and it wasn’t flexible enough. I ended up querying the data directly and copy & paste to Excel where I could use pivot charting. What a great feature of Excel — it let me organize the data easily and visualize the problems to management, system and storage administrator and other DBA’s. I moved on and didn’t have time to continue this project, clean it up and put into public domain. I’ve still had it in my mind but there is no need now since Tanel already did far better job. He put the first version of the Sesspack on his web-site about half a year ago. What excited me more this time was the integration with Excel that he did — what a powerful but simple tool in the hands of a smart DBA. I’m looking forward to use it when it becomes available on his web-site.
Update: Tanel put the material on his web-site here.
(more…)

First of all “the before” time is over — I’m done with my presentation. It’s been the first slot of the day — 8:30 and Cary Milsap was presenting in another hall so what chances do I have to get people in? It turned out that some people actually did show up and quite a few considering the circumstances.

I have mixed feeling on the results. The presentation started very well and I managed to wake people up at the very beginning — thanks to the “equipment” I had at hands (thanks Marco and Riyaj!). You can spot one of them on the photo (thanks for the photo Marco):

(more…)