Travelling in a Wheelchair

It’s that time of the year again, when one of the best grass roots Oracle user group conferences takes place, the Rocky Mountain Oracle User Group Training Days in Denver Colorado. I’ve been privileged enough to present at this conference several times in the past, and always have an absolute blast at it, so I try to submit a few papers each year. This year, I had three papers accepted. Two of them were designed (more...)

No Oracle instances were discovered do you want to enter one

While try to configure Backup exec agent in database server

“No Oracle instances were discovered do you want to enter one”


add the instance value in /etc/oratab

Anyone need remote help?

Does anyone know of any good contracts that would support mostly remote work?

I started this blog years ago with the idea that it would be a good place to search for work should I ever need it. I think the time has come to just ask to see if projects are available through this avenue. If you know of anything, I would love to speak with you. Would you mind commenting below or sending (more...)

GROUP BY – wrong results in

I encountered this during some testing – the optimizer can be a little overzealous when it encounters nested group-by’s

SQL> create table T ( ts number not null, c char(10));
Table created.
SQL> insert into T
  2  select 100+dbms_random.value(1,50),'x'
  3  from ( select 1 from dual  connect by level < 1000 ),
  4       ( select 1 from dual  connect by level < 1000 )
  5  /
998001 rows created.
SQL> commit;
Commit complete.

High CPU during I/O (continued)

Last week I posted a blog on high CPU utilization during I/O. The blog title contained a question mark because it seemed like there were more questions than answers. Were the CPU utilization numbers real or just an instrumentation artifact? Were they distorted by double-counting? If real, where was it coming from? About a dozen top experts participated in that discussion, and everybody had a different theory. I’ve spent some time looking at the problem (more...)

Data Center of the Future – now



photo by youflavio

In a recent blog post Eric D. Brown defined an Agile Data Center as

An Agile Data Center is one that allows organizations to efficiently and effectively add, remove and change services at the speed of the business, not the speed of technology - Eric D. Brown

In follow up post he said that a Agile Data Center could be implemented by Software Defined Data Center (SDDC) for example using machine (more...)

High CPU during I/O?

Yesterday, I posted a trace file that seemed odd to me Twitter. This resulted in a very lively discussion, and several very interesting theories were put forward. Even though the issue hasn’t been solved yet, I would like to post a summary of this discussion (plus my findings) so that more people would be able to give their inputs. Also, some of the theories put forward to explain the observed anomaly are very interesting on (more...) by Clive Bostock


This is a reposting of an old blog post that was on but is no longer accessible

More trace file analyzer tools at

Related blog post: Oracle “Physical I/O” ? not always physical

Often when I have a 10046 trace file, especially when looking at I/O issues, I want a histogram of I/O response time.  To get I/O response time I’ve hacked out incomple awk scripts from time to time, (more...)

Put Delphix on your laptop at Oracle Jan 28 !



Create an army of clone databases and applications in minutes


Tomorrow Jan 28 we will be installing Delphix on people’s laptops at the BIWA conference at Oracle conference center at Oracle head quarters in Redwood Shores.


  • Laptop, either
    • Mac: VMware Fusion or VirtualBox
    • Linux: VMware Fusion or VirtualBox
    • Windows: VMware Workstation or VirtualBox
  • at least 8 GB RAM
  • at least 50 GB free disk space, but preferably 100 GB free
  • at least 2 Ghz CPU, (more...)

Succeeding with Test Data Management



Screen Shot 2015-01-26 at 6.00.46 PM
Test data management is difficult, time consuming and expensive leading to incorrect implementation of test data management and significant losses in revenue from high QA costs to bugs in production. Fortunately there is a solution that alleviates the majority of the huge resource, time and planning of conventional test data management and that new technology is called data virtualization.
Dependable QA testing requires that code be tested on data that represents the data (more...)

5 ways to boost your career with Social Media


Photo by Kevin Dooley

If you are in the Bay Area tomorrow, Jan 27, come see myself, Yann Ropars and Yury Velikanov talk about how to leverage social media to boost your career. We will be talking at Oracle head quarters at the NoCOUG/BIWA conference at 2:30 pm 

Why use social media as an IT technician? Because

vibrant social networks are key to landing jobs, moving forward in your career, and securing personal happiness – (more...)

You’re Cleverer Than You Think

I often train experienced developers in new tools, and I’ve found that most underestimate what they can do – their actual skill level is higher than their own perceived skill level.

Skill development

This is different from new developers, who tend to overestimate their skills.

The reason this happens to most experienced people is the “loss of control” feeling overcomes the feeling of accomplishment. If you are very skilled with one tool, you are acutely aware that (more...)


Disjunction (logical OR) is known to cause various performance problems, from extreme parse times (e.g. here) to sub-optimal plans. A common solution to such problems is getting rid of OR’s by “OR expansion” (i.e. rewrite via UNION ALL), although it doesn’t work in 100% cases. In this post, I will consider an example of an OR problem that can be solved differently.

Here is the setup:

create table t(
   id number,
   x  (more...)

Share your interesting SQL or PL/SQL experience on stage, on camera, or in print

If you have had interesting experiences with SQL or PL/SQL in your career, here’s your opportunity to share them on stage, on camera, or in print. Send your stories to and we’ll forward them to the SQL evangelists team headed up by Steven Feuerstein. You may be selected to tell your stories on stage at the YesSQL! presentation at the winter conference next Tuesday or your stories may be recorded on camera or (more...)

Hardware is Cheap, Developers are Expensive

When advising customers on ADF projects, I often find development environments where many or all developers are working against the same database. That introduces a hard dependency between different parts of the project – if one developer deploys a defective PL/SQL package to the database, nobody else can run the application.

This approach made sense back when hardware was expensive and databases had to be managed by high priests in glass-walled, climate-controlled rooms. Today, you (more...)

Moving from Procedural to Set-Based Thinking

Most people who are new to working with databases tend to think procedurally. That is: I have a table that I need to update, so:

  • Find the first row
  • Update the relevant columns with the relevant values
  • Find the next row
  • Update the relevant columns with the relevant values
  • Find the last row
  • Update the relevant columns with the relevant values

People who are familiar with databases and set-based thinking would simply do:

Oracle Node.js Database Driver

I’ve been eagerly awaiting the first release of the Official Oracle Node.js Driver and Christopher Jones (@ghrd) just tweeted this –


So I hopped over to the Github repository to take a look and try it out…

…I’m very impressed so far…

Back in 2014, I presented at KScope on “Oracle APEX + Node.JS – A Primer” where I showed many demos on just how you can integrate Node.JS (more...)

Free Version of Delphix !

Delphix is now available for  30 day trial direct download ! ( if you would like a longer version please contact me at year trials and even indefinite trials  potential possible for partners, bloggers, Oracle Aces etc)

Just got to the

The Delphix download trial consists of 3 pre-configured virtual machines downloadable as OVA files

Inappropriate behaviour

You pick up little funny things in the day to day with Oracle.

Like this one when you try to drop a tablespace with a queue table in it:

drop tablespace MY_TSPACE including contents
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-24005: Inappropriate utilities used to perform DDL on AQ table

You would think that since you’ve asked to drop everything, that well…everything could be dropped, but (more...)

Top 3 criteria to choose a data virtualization solution 

mirror_reflection_ copy

Data virtualization solutions also known as Copy Data Management (CDM), Copy Data Virtualization (CDV) and Data Virtualization Appliances (DVA) are rising rapidly as over 100 of the Fortune 500 have adopted data virtualization solutions between 2010 and end of 2014. Adoption is hardly surprising given that data virtualization reduces the time to provision copies of large data sets from days down to minutes and eliminates most of the space required (more...)