During the years I heard lots of stories about sizing the Oracle Database Buffer Cache. Oracle introduced in Oracle 8i (8.1.7) the view V$DB _CACHE_ADVICE. According the documentation this view shows IO’s that would be performed at various cache sizes from 10% to 200% of the current size. For example (GV$DB_CACHE_ADVISE):
The thing what is crossing my mind all the time is the question, will a system really react the way the advisor is predicting? This question is a very obvious question of course and in this post I like to place a nice little discussion in place.
As you know I have just started my own blog and I realized that sometimes pretty simple things can be really handy to know. Some time ago I found out by accident that Oracle 11G database has a nice feature to find out the available underscore parameters in the pfile/spfile (there are more underscore parameters, but these are really dangerous).
=================== DISCLAIMER ===================
The usage of underscore parameters is officially prohibited. Underscore parameters should only be used after having instructions from Oracle Support. The usage from underscore parameters without having these instructions can lead to an unsupported Oracle environment. Also instability, crashes or even corruptions can be caused by usage of these parameters. So please use the information in this post with care.
These parameters can be easily obtained by giving the following command on the sql prompt as shown here:
At Oracle Open World I had after the keynote from Larry Ellison the opportunity to see the machines where everybody was talking about. Marco (the XMLDB guy) found out where they were, so Marco and me went to Moscone North and found the machines in their full glory… (a bit exaggeration, but to be honest as a former worker at IBM it still gives me a good feeling to see this kind of technology…).
At the moment we really went close to the machines, a security officer gave us some signs that we were not allowed to cross a line I didn’t see before. Anyway still looking at the machines from a small distance and making many pictures…
Sunday 21 September 2008 at Oracle Open World, I had the opportunity to present my method “GAPP” once more (HOTSOS 2008 and Planboard may 2008). This time I also mentioned how the method can be used with Service Oriented Architectures (SOA). For people not knowing what “GAPP” is all about I give a small introduction to the method. I also like to tell you why I started with “GAPP” in the first place and what the added value is of the method above other methods.
“GAPP” means General Approach Performance Profiling and can be used to find out where in your architecture the most wait time variance can be explained from your business process. “GAPP” makes it possible with very little data, in higly complex technical infrastructures, still be able to find the performance bottlenecks for a specific business process. The nice thing about the method is that it is not only able to pinpoint a bottleneck which is already there, it is also able to pinpoint a future bottleneck in a normal running system. This is something what only “GAPP” can do.
What makes “GAPP” special:
- The method can analyse the full infrastructure, so from front-end to back-end
- The method is not focussing on one piece of the infrastructure, like only the database
- The method is able to predict how the response time of a business process will react on changes in involved factors
- The method is able to predict when a certain bottleneck will evolve to a real problem
The third of march 2008 I had the opportunity to present my developed performance profiling approach called “GAPP” at the HOTSOS Symposium 2008 in Dallas. “GAPP” is an abbreviation of “General Approach Performance Profiling” and is based on data mining of all kind of gathered system statistics (but also other data is possible).
The presentation went well and a lot of people attended my presentation. I got a lot of nice criticism and was questioned a lot by Dr. Neil Gunther. Before and after the presentation I had a lot of nice discussion with him and he even offered to help me make this approach even bigger. For me this was a real honor and I really was very happy with his input.
Also a lot of other “important” people attended the presentation, like Anjo Kolk, James Morle, Cary Millsap, Jeroen Evers, Toon Koppelaars and many others. I personally was very happy to have the chance to present for such an audience, and was very happy with their reactions and criticism. I personal think that the HOTSOS Symposium is “The Place” for performance in the world. Continue reading