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December 2011

IOT Trap

In a recent question on OTN someone asked why Oracle had put some columns into the overflow segment of an IOT when they had specified that they should be in the main index section (the “IOT_TOP”) by using the including clause.

The answer is simple and devious; there’s a little trap hidden in the including clause. It tells Oracle which columns to include, but it gets applied only after Oracle has re-arranged the column ordering (internally) to put the primary key columns first. The OP had put the last column of the primary key AFTER the dozen columns in the table that he wanted in the index section, but Oracle moved that column to the fifth position in the internal table definition, so didn’t include the desired 10 extra columns.

RMOUG Training Days 2012

RMOUG Training Days 2012
Event date: 
Tue, 2012-02-14 - Thu, 2012-02-16

One of the largest Oracle user group conferences in the world, the "Training Days 2012" conference presented by the Rocky Mountain Oracle Users Group (http://www.RMOUG.org) is two days on Wednesday and Thursday (15-16 Feb), consisting of more than 140 presentations by more than 100 of the top speakers in the world.  Registration for this conference, from as low as US$265 - US$340 for early registration, is an incredible educational value.  Click here to register for this event.
 

Right Deep, Left Deep and Bushy Joins

At UKOUG someone asked me if DB Optimizer’s VST diagrams could deal with left deep verses right deep execution plans. What is right deep verses left deep? Good question. In join trees (not VST) the object on the left is acted upon first then the object on the right.  Below are left deep and right deep examples of the same query, showing

Cary Millsap : Mastering Oracle Trace Data…

I was ribbing Cary about missing his unconference session (due to migraine and alarm malfunction). Lenz Grimmer and I both tweeted him to see where he was and in return we received this message in reply.

Very generous indeed. Unfortunately Lenz was flying home so he couldn’t make it. I had a conversation with Cary about it saying I wanted to come, but felt weird about accepting a freebie, so I thanked him for the offer and left it at that.

UKOUG 2011: Days 1 – 3…

I went to lots of good presentations over the three days.

Day 1:

  • SQL Tuning – Kyle Hailey
  • Clonedb – Me (not counting myself in the “good” list, just placing myself in the timetable)
  • OakTable Talks
  • Emerging Trends in RAC – Julian Dyke
  • Upgrading your Cluster to 11gR2 – Martin Bach
  • Learning about life through business and software – Cary Millsap

Day 2:

  • NFS Tuning – Kyle Hailey
  • OakTable Talks
  • RAC Attack – Organized by Jeremy Schneider (I spent the rest of the day helping out here)

Day 3:

Recent SPARC T4-4 TPC-H Results Prove Oracle Can Do Better Than…Oracle! Part II.

My recent post entitled Recent SPARC T4-4 TPC-H Benchmark Results. Proving Bandwidth! But What Storage? provoked the following comment/question  from a reader:

Does this summarize your point(s)?

TPC-H produces a number which is a reflection of (hourly?!?) system throughput.

System throughput may not be indicative of system “performance” to its uses b/c users are typically most intersted in response time. Thus, TPC-H is a easily mis-used benchmark for comparing real world performance.

Christmas Explain Plan Patterns

Here’s a lovely Candy Striped pattern in an Explain Plan. Looks like the traditional Christmas candy canes. Just in time for the Holiday Season!

Test Data

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
;

Oracle Core

As Martin I had a pleasure to “unofficially” review Jonathan’s latest book, Oracle Core. It was my first experience in the area of printed content. If you want to know little bit more how the process went, my opinion on the book and what to expect from it – I’ll try to cover these points here.

The cause for and against the Exadata simulator

I am on my way back from the best UKOUG conference I ever attended, unfortunately a lot earlier than planned. Before I start forgetting all these great moments it is time to write them up. To make use of James Morle’s words: if you weren’t there, you lose. I couldn’t agree more!

The Oak Table Network organised “Oak Table Sunday”, a hugely successful event on Sunday afternoon. This event featured some of the brightest Oracle minds, and thanks to a very relaxed atmosphere made it all a truly exceptional experience. I have to say that the audience was quite illustrious too-I didn’t recognise Paul Vallee from Pythian with his Movember moustache at first and to my great joy I finally met Piet de Visser again. After exchanging a few words with them I ran into so many people it was just great!