Welcome to Soocs, the premier Oracle database consultancy that specializes in the Oracle database technology stack.
The independent consultancy is based in Germany, but I operate globally, with a focus on serving clients in Europe and NAFTA. My expertise in the Oracle database core sets me apart from others, as I excel in resolving complex issues that others often give up on. Don't just take my word for it - explore my website to discover my blog, publications and client reviews. Experience the Soocs difference for yourself and see why I am the go-to expert for all things related to Oracle database performance and troubleshooting.

Silver bullets may be appropriate for hunting werewolves but not for fixing Oracle database or application performance issues.

As your trusted partner, I offer reliable solutions for your mission-critical issues and "must not fail" projects. I prioritize your needs and concerns, without getting bogged down in political games or wasting precious time. My expertise is both affordable and flexible, making it easy to access the support you need. Plus, all of my services are provided with the utmost confidentiality.

Oracle Database & Application Performance

Oracle Database & Application Performance

My performance services are founded on a systematic and scientific approach called "Method-R". This approach focuses on improving end-user response times to maximize economic value for your business and deliver reliable performance forecasts.

My Oracle performance tuning service offers top-notch database, application (PL/SQL or client-side code) and SQL statement analysis including troubleshooting of the cost-based optimizer (CBO), logical and physical data model design, application instrumentation, scalability benchmarking, and optimization of operating system configurations (primarily AIX and Linux) for Oracle database systems. With extensive experience in SAP on Oracle, I provide specialized Oracle database services for SAP, including performance analysis and tuning of SAP systems, SAP applications, and R3load-based migrations.

In addition, I offer customized performance tuning workshops for individual clients or public online training sessions.
Oracle Database & Operating System Troubleshooting

Oracle Database Internals & Operating System Troubleshooting

I specialize in providing troubleshooting services for Oracle RDBMS core problems and operating system integration issues, specifically on AIX and Linux. My expertise involves extensive research and debugging using tools such as eBPF, DTrace, GDB, and SystemTap, which allows me to offer rare insights into the internals of Oracle RDBMS.

In situations where business-critical issues arise, such as shared pool issues, sporadic memory leaks, general memory issues, unexpected ORA errors, unpredictable I/O behavior, database crashes with core dump, or a stuck database, my knowledge and skills can prove invaluable in identifying the root cause and providing a solution or a work-around. My services also include assisting clients in understanding the corresponding Oracle core component, creating an isolated and reproducible test case for Oracle support if necessary, or researching specific issues from scratch.

Additionally, I offer client-specific Oracle internals workshops or public online trainings to share my knowledge and expertise with others.

If you have any questions about my services or need assistance with an issue, please don't hesitate to contact me directly.
I am usually available at short notice and would be happy to assist you.

About Me & Company


I am Stefan Koehler, an independent Oracle database consultant and the founder of Soocs. My career began in 2001 with an apprenticeship in "IT specialist/system integration," which I completed as one of the top performers in my cohort. I then spent two years working as a *nix admin with a focus on IBM AIX and Linux, as well as Oracle DBA before moving into the SAP space. There, I honed my expertise in Oracle databases and SAP performance tuning. In 2011, I founded Soocs to provide specialized and independent consulting services for Oracle database performance tuning and internals troubleshooting in mission-critical environments.

For over 22 years, I have been passionate about Oracle and specialize in performance tuning and troubleshooting, with a particular focus on Oracle's cost-based optimizer (CBO) and database internals. I'm not content with merely understanding how an Oracle database feature works; I'm driven to understand how it is implemented in minute detail. This has led me to research many Oracle database internals for educational purposes or in response to clients' needs. I'm also well-versed in Oracle High Availability and Oracle Backup and Recovery, rounding out my skill set.

Today, I primarily work as an independent Oracle database performance consultant and researcher in very large mission critical environments for market-leading companies or multi-billion dollar enterprises in various industries worldwide. I support my clients by helping them understand and solve complex Oracle performance issues and troubleshoot nontrivial database issues on a short-term contract basis.

Sharing knowledge is one of my primary values when working with clients or engaging with the community. I regularly share my experiences, findings, and knowledge through my blog and my participation in the DOAG, Oracle-L, Oracle Technology Network, SAP Community Network, and Twitter.

In 2015, I received a significant honor in my professional career when I was invited to join the well-known OakTable network. This informal organization is composed of Oracle experts from around the world who believe in better ways of administering and developing Oracle-based systems. In the past, I was honored as an Oracle ACE by Oracle's ACE program over several years. Today, I proudly hold the title of Oracle ACE Alum.
Stefan Koehler

Contact & Tax Information

  •  Stefan Koehler
  •  Spessartstraße 2, DE-97249 Eisingen, Germany
  •  +49 (0) 172 / 1796830
Clients & Reviews
Due to confidentiality agreements, particularly with my US clients, the list below only includes a partial selection of my clients. For more detailed information, please reach out to me.
Stefan is a genuine Oracle database expert with in-depth knowledge and understanding of database internals and optimizer. He is able to efficiently work out a straightforward solution to all kind of different problems around the database, even complex performance bottlenecks, hanging issues and system crashes. If you need a quick solution for an urgent issue with an Oracle database, he is a right consultant to hire.

Nenad Noveljic

Head of Databases & Executive Director, Bank Vontobel AG, Switzerland
Stefan's in-depth knowledge of the Oracle database, combined with his ability to delve deep into Linux and storage subsystem configuration has proved invaluable to our company. We particularly appreciate the convenience to being able to collaborate with him via Slack.

Patrick Jolliffe

Manager, Li & Fung Limited, Hong Kong
Stefan is a brilliant Oracle Consultant who knows not only the Oracle DB, especially the undocumented depths down to individual C-functions, but also the underlying operating systems, in our case IBM AIX. It is especially this combination that makes him so valuable to us and has saved us more than once. You recognize that he spends a lot of time with research and education. He knows every article, every tool and has contact to everyone in the Oracle community who is important. All this leads again and again to problem solutions in an impressively short time at a very fair price.

Bernd Tomczak

Head of Core System Platform, Debeka VVaG, Germany


Date Time Training title Details & Purchase
Tuesday, June 13, 2017 3:00 PM to 7:00 PM (CEST) Online class: Advanced Oracle internals & troubleshooting - Shared Pool Details about past event

Public Appearances

When Where Event Talks
September 28 - 29, 2022 Zurich, CHE Trivadis Performance Days 2022 Troubleshooting Oracle I/O Performance Issues
September 9 - 10, 2022 Wroclaw, POL POUG Advanced Oracle Database Troubleshooting - Finding and Fixing A Bug On Your Own
November 17 - 19, 2020 Nuremberg, DEU DOAG 2020 Conference In-Depth RDBMS Hacking Session: Troubleshooting I/O Latenz
June 30, 2020 Online AOUG - Let's go online! Oracle RDBMS Hacking Session: Erwarte das Unerwartete
June 18, 2020 Nuremberg, DEU Regional DOAG group meeting Oracle RDBMS Hacking Session: Erwarte das Unerwartete
April 23, 2020 Munich, DEU Regional DOAG group meeting Systematisches Performance Tuning mit freien/kostenlosen 3rd Party Tools
March 27, 2020 Warsaw, POL POUG Workshop Systematic performance troubleshooting with (free) 3rd party tools
November 19 - 21, 2019 Nuremberg, DEU DOAG 2019 Conference Systematisches Performance Tuning mit freien 3rd Party Tools
September 26 - 27, 2019 Zurich, CHE Trivadis Performance Days 2019 Troubleshooting with Oracle's Kernel Debug, Diagnostics and Tracing Infrastructure
September 6 - 7, 2019 Wroclaw, POL POUG Double Feature & Extended Cut: Oracle's kernel debug, diagnostics & tracing infrastructure
August 20, 2019 Stockholm, SWE SWE OUG - Oracle Tech Talk Where is Waldo? The memory leak edition
July 18, 2019 Nuremberg, DEU Regional DOAG group meeting Systematisches Oracle Performance Tuning mit (kostenlosen) 3rd Party Tools
May 23, 2019 Würzburg, DEU Regional DOAG group meeting Oracle Kernel Troubleshooting
January 11, 2019 Online DOAG Database Webinar Wo ist Walter? Die 0x Memory Leak Edition
November 20 - 22, 2018 Nuremberg, DEU DOAG 2018 Conference Oracle's kernel debug, diagnostics & tracing infrastructure
September 7 - 8, 2018 Sopot, POL POUG Where is Waldo? The 0x memory leak edition - Published by Geek Press
June 12, 2018 Vienna, AUT AOUG 2018 Conference Under the hood of dynamic and adaptive database features
June 11, 2018 Munich, DEU Regional DOAG group meeting Under the hood of dynamic and adaptive database features
March 15, 2018 Nuremberg, DEU Regional DOAG group meeting Under the hood of dynamic and adaptive database features
November 21 - 23, 2017 Nuremberg, DEU DOAG 2017 Conference Under the hood of dynamic and adaptive database features
October 19, 2017 Nuremberg, DEU Regional DOAG group meeting Researching the Oracle core - 3 slides and a lot of internals hacking fun
October 3, 2017 San Francisco, CA, USA Oak Table World 2017 Lightning Talk - Troubleshooting & Fixing Long #PARSE Calls In 10 Minutes
September 1 - 2, 2017 Krakow, POL High Five POUG Researching the Oracle core - 3 slides and a lot of internals hacking fun in 45 minutes
February 27 - March 2, 2017 Dallas, TX, USA Hotsos Symposium 2017 Troubleshooting Oracle performance issues beyond Oracle wait interface
Hacking Oracle's memory - About internals & troubleshooting
November 15 - 18, 2016 Nuremberg, DEU DOAG 2016 Conference Hacking Oracle's memory - About internals & troubleshooting
October 20, 2016 Nuremberg, DEU Regional DOAG group meeting Hacking Oracle's memory - About internals & troubleshooting
September 28 - 29, 2016 Zurich, CHE Trivadis Performance Days 2016 Troubleshooting Oracle performance issues beyond Oracle wait interface
June 16, 2016 Nuremberg, DEU Regional DOAG group meeting Troubleshooting Oracle performance issues beyond Oracle wait interface (Extended Version)
November 17 - 20, 2015 Nuremberg, DEU DOAG 2015 Conference Identifying performance issues beyond Oracle wait interface