January 30, 2012 As we have seen in the past, TKPROF output sometimes lies, and in a recent OTN thread I was reminded of another case or two where TKPROF output may be misleading. In the OTN thread, the original poster (OP) started the thread by asking a simple question about an execution plan that appeared [...]
On February 14-16, I’ll be at the Colorado Convention Center in Denver, Colorado for RMOUG’s Training Days Conference. This is the largest regional Oracle User Conference in North America and attracts presenters from all around the country and the globe. I’ll be presenting:
Presentation Name: Troubleshooting RAC Background Process
Abstract: RAC background process performance is critical to keep the application performance. This session will demo techniques to review the performance of RAC background processes such as LMS, LMD, LMON, etc. using various statistics and UNIX tools. The presentation will also discuss why certain background processes must run in higher priority to maintain the application performance in RAC.
Presentation Name: A Kind and Gentle Introduction to RAC
I’m really pleased to see that Richard Foote has started a series on Index Organized Tables. You can see his introductory post on the topic here. As ever with Richard, he puts in lots of detail and explanation and I’ve been a fan of his blogging style for a long time.
I’ve got a few posts on the topic left to do myself, maybe this competition will spur me to get on and write them!
January 9, 2012 A recent thread in the comp.databases.oracle.server Usenet group brought back memories of when Randolf Geist and I worked on the two chapters for the “Expert Oracle Practices” book. In the chapters, among other things, we demonstrated how to enable 10046 trace files for sessions using various approaches (some of the approaches change the SQL_TRACE, SQL_TRACE_WAITS, [...]
Both an ORACLE-L discussion here and a Stack Exchange post raise essentially the same question which is, paraphrased: What is the performance overhead of datafile autoextend events. The conventional wisdom, with which I agree, is that the overhead is insignificant. However the poster in the stack exchange dialog asked how one would determine this empirically. [...]
One of the easiest ways to understand something is to see a visualization. Looking at Active Session History (ASH) data is no exception and I’ll dive into how to do so with R and how I used R plots to visually present a problem and confirm a hypothesis. But first some background…
Frequently DBAs use the Automatic Workload Repository (AWR) as an entry point for troubleshooting performance problems and in this case the adventure started the same way. In the AWR report Top 5 Timed Foreground Events, the log file sync event was showing up as the #3 event. This needed deeper investigation as often times the cause for longer log file sync times is related to longer log file parallel write times.
December 18, 2011 It seems that I have been quite busy lately with computer related tasks that are not associated with Oracle Database, making it difficult to slow down and focus on items that have a foundation in logic. Today I have had some spare time to dig further into the recently released “Oracle Core” [...]
The UKOUG conference is over for another year – but it has left me with plenty to do and lots of things to investigate. Here’s just one little point that I picked up during one of the 10 minute “Oak Talks” that members of the Oak Table Network were doing in the lunch breaks.
There is a fairly well-known strategy for generating a list of numbers by using a “select from dual … connect by …” query, but I hadn’t realised that there were two ways of using it. The code I’ve usually used is this:
select rownum id from dual connect by rownum <= 4000 ;
But it looks as if most people use it like this:
select rownum id from dual connect by level <= 4000 ;
My good friend (and personal hero) Cary Millsap is doing a series of one day classes around the world — Mastering Oracle Trace Data. One of them is conveniently scheduled in Birmingham Thursday next week right after the UKOUG Conference. It’s not far from the Birmingham ICC where the UKOUG Technology and Business Suite Conference [...]