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November 2009

The Oracle Wait Interface Is Useless (sometimes) – Part One: The Problem Definition

So here we go, this is part one of this experiment in blogging and co-writing. Tanel has actually written some good stuff already for this, but I wanted to try and formalise things under a common title and make it easier to follow between our sites.

I thought it would be logical to start this process by producing a more concrete problem definition, so that’s the focus of this part. It’s unlikely that we will come up with a complete method in this initial work, but hopefully the wheels will at least turn a little by the end of it!

So first of all, why would I dare to say that the Oracle Wait Interface is useless? Well, partly because I quite like titles that are a little bit catchy, and partly because it is indeed sometimes useless. The emphasis is on the word sometimes, though, because the Oracle Wait Interface is still the single most useful feature in any database product. Wow – that’s quite a claim, isn’t it? This isn’t the place to fully explain why that is, and many others have written great works on this subject already. Check out Cary Millsap’s works, notably his book, Optimizing Oracle Performance, which focuses in great detail on this subject. For the sake of this article, however, here’s why it is so useful: It tells you where the time goes. Think about it: If something is running too slowly, knowing where the time is used up is the single piece of information required to focus on the right subject for tuning.

another (possible) nonsense correlation

I was reading news stories on Reuter's this morning and came across a new study. Researchers have determined that men who work in unchallenging jobs with little control over their future tend to be less active off the job as well.Now, I don't doubt that there is a relationship between a passive work role and the amount of activity someone engages in off the job. However there are a few quotes

Explaining the number of Consistent Gets

Last week I received an email from a friend, who wishes to remain anonymous, with the question why Oracle needed 8 consistent gets to perform a full table scan on a table where all the rows are stored in just one data block. There are several possibilities that can cause this and that is what [...]

Starting Oracle Blog

Quite a long time ago I was tempted to start blogging about Oracle and then I decided just not to do that but rather I started to blog about my flying around Europe to present at Oracle conferences. However, I created the blog but never activated. The nomination for Oracle ACE changed this decision and I'll try to write about technical stuff from time to time, but don't expect that I will be so active as some of Oracle bloggers.

Detecting and Fixing Row Migration

In my previous posting, I discussed how migrated rows led to latch connection problems on a system. In this entry I will explain how I identified and removed the migrated rows, and correctly set PCTFREE on each table so that the problem will not recur.

RHEV (Red Hat Enterprise Virtualization) is out!!! :)

The company I work for, SQL*Wizard,  is a RedHat Advanced Business Partner so I was lucky to get my hands dirty on the BETA release of RHEV, also a pleasure to work with Siva Shunmugam (Sr. Solutions Architect@RedHat & RHCA). I must say, KVM is so fast… plus the RHEV manager is so cool as a management platform :)

Soon I’ll have some Virtualization related posts about my experiences RHEV-iiinnggg…..

RHEV

11gR2: materialized view logs changes

In this post we are going to discuss some 11gR2 changes to materialized view logs that are aimed at increasing the performance of the fast-refresh engine of materialized views (MVs), especially the on-commit variant.
The MV logs, in 10gr2, now comes in two flavours: the traditional (and still the default) timestamp-based one and the brand [...]

Listing files with the external table preprocessor in 11g

Using the 11g external table preprocessor to get directory listings in SQL. October 2009