Christian Bilien’s Oracle performance and tuning blog

January 11, 2008

Tag flood

Filed under: Off topic — christianbilien @ 4:08 pm


Amid the tag furry, I was tagged some days ago by Jeff Moss so I’ll have to give some pieces of information about myself presumably of low interest to most. I had not put any personal information on my blog, so here are 8 of them which I’ll keep short anyway:

  • I come from a small town in Brittany, France, located almost as far west as conceivable before falling off a cliff. My parents spoke Breton before they learned French at school.
  • I was an undecided student, who spent 6 years studying Mathematics and Physics followed by a year in management studies before realizing that what he was interested in was History.
  • So I read a lot, predominantly History and current affairs books.The last book I read: The Great War for Civilization by Robert Fisk (highly controversial in the USA, less in the UK).
  • I volunteered to join the army paratroopers (national service was mandatory for boys only at the time –how unjust-), a formative experience to say the least.
  • I love performance tuning and modeling but I am not a geek as such. I have no interest whatsoever in “intelligent” phones, PDAs, games, and so on.
  • I feel depressed unless I run at least 40km a week, and I also love diving, sailing and swimming.
  • I love traveling, especially by foot in the deserts. The landscapes that most impressed me were in the Namib Desert. Most unsettling experience abroad: living in the UK for two years (I’m joking here – I had great time and was feeling half English when I left).
  • Last bullet, well what else could I say? How about “I hate DIY, much to my wife’s dismay”?

Well, thanks for reaching this point.


I am quite a late comer to the tag thing: I have a feeling that all the oracle blogs I read have already been tagged, so I’ll stop the chain here.



August 13, 2007

Summer time statistics

Filed under: Non-technical,Off topic — christianbilien @ 9:47 am

Just back from some long, laptop-free vacations. I’ll slowly resume blogging as soon as I have cleared up the pile of unread mails. A couple of casual news before getting back to more serious matters:

My blog just reached 10000 hits this morning, a modest but still rewarding accomplishment of a 7 months existence. I had an audience bump a few weeks ago when some excellent well-known bloggers and book writer (Jeff Moss, Doug Burns, Jonathan Lewis, Jeremy Schneider – I hope those I did not name won’t be offended) were kind enough to reference my blog. The RAC entries get by far the most hits, followed by the PGA and storage array related posts. Solaris DISM/ISM posts are also in the top league. Most comments are targeted at storage array cache and raid stuff.

I found in my post office mailbox the awaited “Forecasting Oracle Performance” Craig Shallahamer published at Apress. I indulge a craving for mathematical forecasting so I hope this book bridges the gap between Oracle’s own data (AWR and ASH) and the queuing theory.

March 14, 2007

SQL can execute in wrong schema (10.2)

Filed under: Off topic,Oracle — christianbilien @ 4:54 pm

Symptoms are: wrong results from SELECT AND data corruption for DML

Although this post is off-topic, I think it is worth sharing one of the nastiest Oracle bug I ever encountered (I am not one of the Oracle pioneer, but I have nonetheless seen a number of them in my life). This is documented in Note:392673.1, which says it is only appearing in 10.1, (for which the manifestations are very rare), but with a much higher chance of occurring in 10.2.

This problem can occur only if all of the following are true:

  • The SQL statement refers to some object without using a fully qualified object name
  • The unqualified object name resolves to a different underlying object for different users.
  • Sessions in different schemas execute IDENTICAL SQL sentences

The note says that the problem is related to reload of aged out cursors, and indeed I experienced it because statistics were calculated before the above conditions were met.

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