zondag 14 augustus 2011

Nice scenario

I received the following problem in Oracle Support that baffled me for some time.

Environment: Rdbms Application Express

Error in the browser:
Unable To Fetch Authentication_scheme In Application.

Error in the webserver log files:
ORA-06512: at "APEX_040000.WWV_FLOW", line xx
ORA-06512: at "APEX_040000.WWV_FLOW", line xx
ORA-06512: at "APEX_040000.F", line xx
ORA-06512: at "APEX_040000.F", line xx
ORA-06512: at line xx
ORA-20867: ORA-06502: PL/SQL: numeric or value error: character string buffer to small

Above error is also described in the known issues against Application Express Release 4.0.2
Known issues in APEX 4.0.2

Solution: Apply the patch for bug 5890966 (related bug) or apply the Patch 6 on Windows Platforms (if on Windows Platforms) or apply the database patch set or upgrade to 11gR1 or later.

But after applying the necessary patches the problem was not fixed yet.

Received the application without customer data. So a plain sql file.
Stripped the appliction completely.
At the end, I only had one page left.

Tried to create the most simple testcase as possible so replaced the tables used with the demo tables of Oracle DEPT and EMP.
Changed the authentication schema to application express.
Problem still reproduced.

Removed the form on the table and created a 'dummy HTML' region instead.
Tested the application:

After logging in, I received the ORA-06502 error
Could not write to error page

Checked the TAB pages and indeed, the problem was caused by the amount of TAB pages used!

I was completely in the wrong direction because of the error message generated by the system.
Now, I can understand the error message generated by the system!
By eliminating, I was able to find the real underlying cause of the problem.

zondag 29 mei 2011

DBA Symposium at the 17th of May

At the 17th of May, I presented at the DBA symposium in the Netherlands.

There were ten technical sessions spread over two parallel tracks.
Different Oracle DBA people shared their experiences with the participants.
They showed how to recognize, prevent and solve problems.

For me, it was the first time to deliver a presentation for only Oracle DBA people.
Normally, I present for Oracle Developers and therefore an extra challenge for me!

I presented about Application Express.
Application Express is very popular in the Netherlands.
An Oracle DBA needs to know were to take care of when dealing with application express.

In autumn of this year, a next DBA symposium will be organized.
I hope to meet you there.

Information about planboard symposium can be found here:
DBA Symposium.

zaterdag 14 mei 2011

Bulgarian User Group Conference in Sandanski

Presented at the Bulgarian Oracle User Group in Sandanski.
Sandanski is the warmest and sunniest town in Bulgaria.

Around three hundred people attended the conference.
There were three parallel sessions available.
For me, a nice opportunity to broadening my knowledge in database area. I also very interested in DBA related stuff!
So next week, I am going to install Application Express in a RAC instance.

One of the sessions, I attended was the session from Daniel Morgan.
To increase your Pl/sql knowledge it is worth it to check the following website. Morgans Library.

Today, I attended sessions from Chris Date. Everybody of you has to recognize this name. Chris Date.

It was a very valuable conference and I did learn a lot.

I need to mention that the whole conference is very well organized, and that I will come back to Bulgaria!

Thanks a lot for the very warm welcome!

dinsdag 5 april 2011

Book Review

Beginning Oracle Application Express 4
Authors: Doug Gault, Karen Cannell, Patrick Cimolini, Martin Giffy D’Souza and Tim St. Hilaire

If you are thinking about developing a product with Application Express this book is a great place to start. It is a complete hands-on book. You will work through the examples and exercises. Example code is available at the website from the publisher. ( Downloadable code and exercises make the book very valuable for learning Application Express. It is really practical and covering almost all the essential application development aspects. You will learn Step by Step from this book with little knowledge of PL/SQL, HTML and JavaScript.

A ticket system for a help desk is created from scratch. In every chapter of the book, a part of the help system is built.
The book starts by making a description of the requirements of the help desk system and to create a database design. This book also covers the steps of creating an entity relationship diagram. Good database design is the key to creating a successful application, especially with Application Express in mind. The necessary database tables used in the ERD are created in Sql*workshop. Sql*workshop and not the ERD tool is used because the objects are created from scratch.
With the basic data created, a shell is generated for the ticket system. This will be done with the options available in Application Express. After the shell is created for the application, the application is extended with forms, reports, and charts. The strength of this book is that the theoretical part is completely integrated in the exercises. This makes the book even more valuable.
When the basic part of the application is built, there is also a chapter about more advanced techniques within forms and reports. It helps to understand Application Express even better and look behind the scenes.
Programmatic elements in Application Express can provide both simple and complex features to the Application Express framework. So the help desk application is extended with conditions, validations on item level and page level, tabular form validations, computations and processes and dynamic actions.

Security in an application is often an afterthought. This book covers this very important topic. The key features of security available within Application Express are added to the application. Authentication is added to the helpdesk application by making use of a customized authentication scheme. The scheme is used to allow control over users who access the sensitive parts of the application. User access is controlled by access control lists. In the help desk application a checksum is added to the URL. This prevents URL tampering.
Once the application is ready, it needs to be deployed. So you learn how to get an application out of the system and to deploy in the production system. Techniques like export, import, and supporting objects are covered.
Websheets is a new feature in Application Express 4. In the book, you will use the features to build a websheet application from scratch. With the application you can manage your corporate soccer team. Websheets is a very nice feature to manage the soccer team. A complete example is provided.
Advanced development features are also highlighted in this book. These tools help when dealing with large applications. Features like page locks, application and page groups are covered.
Of course, your Application Express side needs to be monitored as well. Each time a page is accessed, a log entry is stored. Subjects like activity logging, login attempts, and managing workspaces are covered.
The last chapter in the book is about the team development feature. Team development is a tool for managing Application Express projects. All features like milestones, to-dos, bugs, feedback and features are discussed.

This book is a ‘must’ for people starting to work and develop applications in Application Express.

woensdag 23 maart 2011

Application Express OGH Day

APEX OGH Day at Tuesday the 22th of March
It was an exciting day with 250 attendees.
It is very clear that Application Express is very popular in the Netherlands.

The day started with three plenary sessions.
The first presentation was hosted by Tony Andrews and Nigel Blair.
1500 forms applications were migrated to Oracle Application Express.
A big project but the result is there!
So it is possible!

Hilary Farrell member from the application express development team presented about the new features in application express 4.1.
The most important new features are listed in the statement of direction.

Dimitri Gielis and John Scott gave a helicopter overview "How to deal with big application express projects". This proofs that application express can be used in big projects as well!

After the lunch break there were three parallel sessions available.
A lot of good presentations were available, so it was hard to make a good choice.
My own presentation was dealing about the awareness of security.
You need to think about security from the beginning of a project. Every line of code has consequences for the security. Security is your own responsibility and not from Oracle! Application express is secure, but developers make it insecure.

After my own session, I decided to follow the presentation from John Scott about 'How to build a application express plug-in' A lot of times, I can find a lot of information how to import a plug-in in application express, and rarely the information about the way How to build a plug-in. I am 100% sure that this was useful for everybody in the audience.

The last session of the day I attended was the presentation from Dimitri Gielis about APEX and Locator/Spatial. I can only say, I was impressed and could not believe my eyes and ears about the possibilities available.

It was a very busy day with very good presentations and content.

After the show was closed, I had a very nice dinner with
Alex Nuijten, Learco Brizzi, Christian Rokkita, Peter Raganitsch, Roel Hartman and Jan Leendert.

Thanks all for the nice evening!

maandag 21 februari 2011

Oracle Database Firewall

I want to bring under your attention, the new Oracle Product, the Database Firewall.

Information at Oracle Technology Network about the Database Firewall

External FAQ

donderdag 13 januari 2011

APEX Cookbook signed

Yesterday evening, I received the first official signed cookbook.
This book is written by Michel van Zoest and Marcel van der Plas.

At the picture, you can see Michel van der Zoest because Marcel van der Plas was not available.

Of course, I was very honored to receive the book and I am looking forward to read the complete book.

The book and description of the book.