Upcoming Speaking Engagements

After about four months without any speaking engagements, over the next three months I’ll have the opportunity to speak at several events. I’m looking forward to meet you at one of them!

April 3, I’ll be in Baden-Dättwil to speak about “ASH Analytics” at an event organized by SOUG. Since this is a new presentation covering some stuff that I wrote for the second edition of TOP, I’m looking forward to see how it works.

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CBO Days 2014

CBO Days 2014
The company I work for, Trivadis, is very pleased to organize, on the 10th and 11th of June, an outstanding seminar with top guest speakers in Zurich. This year’s focus will be on the Oracle query optimizer, also known as a cost-based optimizer (CBO).

The query optimizer is not only one of the most complex pieces of software that constitutes the Oracle kernel; it is also one of the most unappreciated. Why? To make the (more...)

Extension Bypassed Because of Missing Histogram

Today, while tuning a fairly complex query experiencing wrong cardinality estimates, I noticed something I was not aware of. Hence, I thought to write this short post to illustrate how to reproduce the problem I experienced…

  • Create the test table (notice the correlation between the data of the two columns):
SQL> CREATE TABLE t
  2  AS
  3  SELECT mod(rownum,50) AS n1, mod(rownum,50) AS n2
  4  FROM dual
  5  CONNECT BY level < = 1000;

Adaptive Plans in Active Session History

Yesterday, during the talk “The Query Optimizer in Oracle Database 12c – What’s New?” at OakTable World UK 2013, an attendee asked me an interesting question that can be summarized as follows: does ASH show the switch of execution plan that takes place for an adaptive plan?

Since (more...)

Oracle ACE Director

Oracle ACE Program

Few days ago Oracle accepted my Oracle ACE Director nomination! In this short post I would like to thank the people that actively supported the nomination.

Special thanks go to Yury Velikanov. When during the last Oracle OpenWorld in San Francisco he discovered I was not part of the Oracle (more...)

System Statistics Gathered in Exadata Mode – When Are They Relevant?

The aim of this post isn’t to explain what the “exadata mode” is. Hence, if you don’t know what it is, before continuing reading have a look to this post published on Kerry Osborne’s blog. The only think I would like to add is that the “exadata mode” is available (more...)

The Broken Statistics: “parse count (total)” and “session cursor cache hits”

The values provided by the “parse count (total)” and “session cursor cache hits” statistics are subject to several bugs. And, what’s worse, for years Oracle didn’t care to fix it. This is my impression, at least.

Then, when few weeks ago I read in the Oracle Support note 13837105.8 (more...)

Scripts to Download Oracle Database 12c Release 1 Documentation

In the past (here and here) I already shared with you the scripts I used to download the documentation related to Oracle Database. The aim of this short post is to provide the scripts I just wrote for the latest version: 12c Release 1.

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Named Notation and SEM_MATCH Table Function

This is a short post about a strange behavior I discovered today…

The fact is that it is not really possible to use the named notation with the SEM_MATCH table function. In fact, even though the parameter’s names can be specified, the order of the parameters overrides the specification done (more...)

ITL Deadlocks (script)

A reader of this blog, VijayS, asked me to share the script I use to demo ITL deadlocks that I mentioned in this comment. Since other readers might be interested, here is the script.

SET TERMOUT ON FEEDBACK ON VERIFY OFF SCAN ON ECHO ON

@connect

SELECT * FROM v$version  (more...)