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July 2012


If you ever wondered how you can convert XML information in v$cell_config on Exadata database servers into relational rows and columns so you can get a nice view of the cell configuration without going into the cell itself then here is a nice piece of SQL which does the job. I'm using celldisks as an example and selecting only a number of column so the output fits nicely on the screen:

SQL> select cellname,
2 name,
3 deviceName,
4 diskType,
5 round(freeSpace/power(1024,3), 2) freeSpace,
6 round(disk_size/power(1024,3), 2) disk_size
7 from (
8 select cellname, XMLTYPE.createXML(confval) confval
9 from v$cell_config
10 where conftype='CELLDISKS'
11 and cellname=''
12 ) v,
13 xmltable('/cli-output/celldisk' passing v.confval
14 columns
15 name varchar(15) path 'name',

Oracle “Physical I/O” ? not always physical

A customer called and wanted to know why the development database was so much slower than production when both databases were on the same type of machine and same type of storage.
To analyze the situation, the same query was run on both databases with

       alter session set events '10046 trace name context forever, level 12';

and sure enough, development (SID=dev) showed average I/O almost twice as slow as production:

July 31 Webinar

Please join me for another Embarcadero sponsored Community Webinar on July 31. This is the first in a series of three webinars. My topics for this triple feature are:

Making SQL Performance Solutions "Stick"
Making Impactful Performance Changes

OTN Tour of Latin America: Costa Rica…

In my previous post I mentioned feeling like a class traitor by paying for someone to do my washing. Well it gets worse. Sheeri and I (but not Debra) got a random upgrade to business class for the 1 hour flight from Honduras to San Jose, Costa Rica. I think that was the first time I’ve ever flown business. So much room. Seats wide enough to fit my ample butt. Tray cleared as soon as you’ve finished eating… A little taste of the good life, before I go back to coach for my big trip home. :)

We got to San Jose in the afternoon and spent a little time by the hotel pool. Not being a sun lover, I spent that time sitting fully dressed on a sun lounger with a towel over my head.

Hello Niall…

… Read an email I received today from Oracle Corporation Hello Niall, I hope you are well. I would like to introduce myself as your Oracle Linux and Oracle Virtual Machine Account representative for I would like to set up a 5 minutes introduction call with you to […]

ANSI Outer 2

A comment on a recent post of mine pointed me to a question on the OTN SQL and PL/SQL Forum where someone had presented a well-written test case of an odd pattern of behaviour in ANSI SQL. I made a couple of brief comments on the thread, but thought it worth highlighting here as well. The scripts to create the required tables (plus a few extras) are all available on OTN. If you create only the four tables needed and all their indexes you will need about 1.3GB of space.

Of Wine and Fish

In my last post touching on my case for Data Engineers, my friend Greg Rahn provided a humorous quote about data from Andy Todd:

“Data matures like wine, applications like fish”

Which, near as I can tell, came from an Open Source Developer’s Conference in Brisbane, 2009 at which Andy talked about, of all things, “Change in Database Schemas and Source Code“.

I’ve dropped Andy an email to see if his presentation is online anywhere, since it touches the topic that is near and dear to my heart.

In this post, though, I’d like to address some of the humor behind the quote — the implication that data gets better as it ages, while applications get worse (and start to smell like stinky fish).

Expert Oracle Exadata (Apress) Translated Into Chinese


Kerry Osborne has a short post to point out that the last book I worked on has been translated into Chinese.  The photo of the book cover looks pretty cool…if only I could read anything except for our names and a few straw English words :-)

This book is a must-read for anyone that wants to cut past the hype an actually learn Exadata.


NFS versus dNFS

Finally got to take Kevin Closson’s SLOB for spin. (BTW can one test dNFS with Orion at all?)
Nice write up on SLOB by Yury Velikanov at Pythian:
Also see Karl Arao’s SLOB cheat sheet.
NEW: see slob on steroids at
I ran into the same issues Pythian came up with

OTN Tour of Latin America: Honduras…

I mentioned the trip to Honduras at the end of my previous post. We landed in Tegucigalpa, Honduras with no dramas. A couple of guys from the University were there to meet us, which was a nice touch.

When getting foreign currency from an ATM, I would suggest you ignore anything Debra Lilley tells you to do. Her expert advice lead me to draw out the equivalent of $10 US, rather than the $100 US I planned to get. We couldn’t even pay for our food. :)