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...

Premature optimization, (probably) because of Donald Knuth’s famous line “premature optimization is the root of all evil,” (see Structured Programming with go to Statements) is, at the very least, a controversial topic. The misconception based on that...

The 11th and 12th of December and, therefore, the CBO Days in Zurich are approaching. Given the high quality of the speakers that accepted my invitation and the number of people that decided to attend the event, in my opinion it will be a blast! By the...

In the last post I discussed a test case generating lot of child cursors. Today I wanted to show you, for the very same test case, that in 11.2 the parse time might increases linearly with the number of child cursors per parent cursor. This is the expected...

The patch set 11.2.0.3 includes a fix for bug# 10187168 which, in reality, is an enhancement request. Its purpose is to artificially limit the number of child cursors that a parent cursor can have. The concept is quite easy: when a parent cursor reaches...

The company I work for, Trivadis, is very pleased to organize, the 11th and 12th of December, 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...

Extended SQL trace (a.k.a. debugging event 10046 at a level higher than 1) is one of the key features provided by Oracle to troubleshoot applications using Oracle Database. For many years the available levels were always the same (4, 8 and 12). In fact...

This is just a short post to point out that the company I work for, Trivadis, is organizing 3 classes with Cary Millsap. The topic, as the title suggests, is Cary’s 1-day class entitled “Mastering Oracle Trace Data”. The following dates and locations...

I regularly use the system-level activity chart available in Enterprise Manager. In my opinion it is a simple and effective way to know how much a specific database is loaded at a specific time. This is for example an interesting way for observing how...

Recently I used the COMMIT_WAIT and COMMIT_LOGGING parameters for solving (or, better, working around) a problem I faced while optimizing a specific task for one of my customers. Since it was the first time I used them in a production system, I thought...

Recently I had to analyse a row lock contention problem that can be illustrated by the following test case: A session (let’s call it #1) creates a table and inserts a row into it (note that “n” is the primary key of the table): SQL> CREATE TABLE...

Most execution plans can be interpreted by following few basic rules (in TOP, Chapter 6, I provide such a list of rules). Nevertheless, there are some special cases. One of them is when an index scan, in addition to the access predicate, has a filter...

The 31st of January and 1st of February 2012 I will present a 2-day seminar about the Oracle query optimizer in Ballerup (DK). The event is organized by Miracle A/S. The content, which is based on the chapters 2, 4, 5, 6, 9 and 10 of my book, is the following...

Challenges and Chances of the 11g Query Optimizer is the name of a presentation I gave at several events (e.g. Trivadis Performance Days, Oracle OpenWorld, DOAG Konferenz, UKOUG Conference) throughout 2011. Its abstract is the following: With every new...

All Trivadis employees meet twice a year near Zurich for a unique conference called TechEvent. The TechEvents, with up to 15 parallel sessions, are among the largest IT conferences in Switzerland. During two days, employees can attend sessions about a...

Recently I was involved in a project where I had to trace the database calls of an application based on Oracle Portal 10.1.4. The basic requirements were the following: Tracing takes place in the production environment Tracing has to be enable for a...

In 2003 I published a paper entitled Debugging PL/SQL and Java Stored Procedures with JPDA. Its aim was to describe how to debug PL/SQL and Java code deployed into the database with JDeveloper 9i. Two weeks ago a reader of my blog, Pradip Kumar Pathy...

The book Der Oracle DBA (Hanser, 2011), which was written in German, is at last available! I say “at last” because the authors worked on this project for not less than two years. Who are the authors? Several colleagues of mine at Trivadis (Mirko Hotzy...

The STATISTICS_LEVEL parameter controls a bunch of features. In addition to the documentation, also the V$STATISTICS_LEVEL view provides a list of the ones it controls. SQL> SELECT statistics_name, description, activation_level 2 FROM v$statistics_level...

At page 189 of TOP I wrote the following piece of text: In summary, with the initialization parameter optimizer_secure_view_merging set to TRUE, the query optimizer checks whether view merging could lead to security issues. If this is the case, no view...

A reader of this blog, Paresh, asked me how I was able to find out the logic behind ITL waits without having access to Oracle code. My reply was: I wrote a test case that reproduce ITL waits and a piece of code that monitors them. Since other readers...

I was just informed that there are still some free seats for the 2-day seminar I will present in Berlin in two weeks (June 7-8). Hence, do not wait too long if you want to join us… The content is based on the chapters 4, 5, 6 and 7 of my book, i...

In recent releases Oracle has silently changed the behavior of ITL waits. The aim of this post it to describe what has changed and why. But, first of all, let’s review some essential concepts about ITLs and ITL waits. Interested Transaction List The...

In this post I pointed out that I like to have a copy of the documentation in PDF format on my notebook. In the same post, and its comments, I also described how I generate the scripts I use to download the files. Recently I updated the scripts and, as...

The company I work for, Trivadis, has organized a 2-day seminar with Cary Millsap, James Morle, Jonathan Lewis and me. It will take place in Zurich the 24-25 of May. If you are interested in topics like the following, do not miss the opportunity…...