After having a good sleep I attended the first session in the morning from George Djerdj Srdanov with a presentation called “How to Get the Most Out of Your I/O Subsystem?”. George dived deep into the I/O subsystem, with the following important subjects:
Different RAID configurations (Read and Write penalties)
Block alignment and recommendation
George Djerdj Srdanov presenting at Hotos 2013
The presentation was good and triggered me to check some things at a customer I am currently working for. In the customer case the block alignment in regard of the online redolog files might be a point of investigation. Continue reading →
Due to a cold or “the bug” some at the symposium called it, I had a very bad night sleep. In the morning I was not able to follow the sessions and I ended up having a good breakfast and released the new white paper and latest presentation to Hotsos for distribution.
At 13:00 I attended the presentation of Dr. N.J.G. Gunther titled “Superlinear Scalability: The Perpetual Motion of Parallel Performance”. Because of his subjects I like to be present at his presentations, although on the other track Gwen Shapira had her first presentation titled “Visualizing Database Performance Using R” which was for me also a subject I would love to be present. The presentation from Neil discussed an important topic regarding the effect of increasing the amount of servers giving better throughput than expected on linearity, this phenomenon has been baptized by Neil as “Superlinear Scalability”. During the past couple of years he struggled to have his USL to fit with this phenomenon and at first he just ignored it, but after seeing the phenomenon more he had to admit the fact it really exists and his USL should be able to cope with it. After a long process he came to the conclusion that his USL is still able to apply if he would loosen the limitation of accepting negative numbers for his alpha parameter (Contention) in his USL. It basically means that by increased number of servers you get a kind of hybrid effect temporary (the throughput has increased with a factor more than expected on the number of added threads based on linear scalability). On a certain moment you still have to face the music and throughput degradation starts to appear due to coherency (Beta parameter in the USL formula). Based on the gathered proof, based on different data sets, he concluded that his USL still is valid, also in situations the “Superlinear Scalability” phenomenon is occurring. As usual Neil really showed in a very good scientific way that his claims were accurate and as he always says, “Models come from God and data comes from the devil!”. If you like to read more you can checkout his blog at: http://perfdynamics.blogspot.nl/2012/11/hotsos-2013-superlinear-scalability.html
Dr. N.J.G. Gunther at Hotsos 2013
After the presentation from Neil it was my turn to give my own presentation as I mentioned earlier, titled “”Method GAPP” Used to Mine OEM 12c Repository and AWR Data”. Continue reading →
It is the first of March 2013 finally… I will travel to Dallas for (one of) the best Oracle performance symposia in the world, Hotsos 2013. The flight to get there will be from Amsterdam to Philadelphia and from Philadelphia to Dallas. Against all odds I will not travel alone but an old Amis colleague and friend Marco Gralike with his colleague will be on the same flight (even going back). After departure from Schiphol at 13:00 in the afternoon, and having our stop in Philadelphia we arrive at the Omni Mandalay Hotel in Las Colinas (Irving / Dallas) at 22:30 local time… This is the real start of an awesome time at this great symposium…
Last week I got the great opportunity to present on Method-GAPP again at the UKOUG 2011 (see presentation of the UKOUG2011). This time the focus in the presentation was partly on the multi linear regression and for the other part especially on AWR data. The multi linear regression makes it possible to get a linear equation to calculate the end user response time, what makes it possible to get a complete breakdown of all involved components in the end user response time as show in the graph below. In the graph the test and modelling from the white paper is shown:
Breakdown of all the involved components for the end-user response time
In the breakdown, the UTILR80 is the utilization of the I/O and the UTILRAU is the utilization of the CPU. The breakdown shows that basically the REST is time which is always there but might be split out in more components if the involved model is enhanced. So more time is explained from the found variance of the end-user (R) response time. Continue reading →
In a lot of cases you like to know which SQL, wait-events, metrics, etc. in AWR is important for your specific end-user process response time. So it could be very well possible that the most important SQL, wait-events, metrics, etc. are show-in up in your “Top Activity” in your OEM grid control and AWR reports are actually not the most important for your end-user process response time.
After you know the share of time of your end-user process is taken by the database server (Method-GAPP primary components), you actual can use all the AWR (and ASH) information as secondary components as input in Method-GAPP (see the white paper). Basically we simply can use the “Data Mining – Explain” step in the method and create a factorial analyses as shown below (see the white paper).