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Stefan Koehler @OracleSK

Independent Oracle performance consultant and researcher. Internals geek. OakTable member. Oracle ACE Alum. Sym42.

Joined October 2014
  • Tweets 6,176
  • Following 76
  • Followers 2,686
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Stefan Koehler@OracleSK
May 11
Rare opportunity to secure guaranteed Oracle Database performance & troubleshooting support Starting from 01 June 2026, I’m opening a limited number of monthly retainer slots for organizations that need reliable Oracle Database expertise without the overhead of a full-time hire.
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Stefan Koehler retweeted
Christoph Lutz@chris_skyflier
3 Aug 2025
lgwr: You have the control gdb: I have the control
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NOPs and shifting trampolines is a fun on-going story all the time (e.g. 2-byte NOP, 0x66 prefixed and eBPF) 🤓 blogs.oracle.com/linux/post/…

Ksplice and Tracing Hooks in the Kernel

An insight to kernel tracing and its interaction with ksplice.

blogs.oracle.com
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Stefan Koehler retweeted
Christoph Lutz@chris_skyflier
23 Jul 2025
If you've ever felt the need to manually control adaptive lgwr features, this gdb script's got you covered: t.ly/lJIW1 😎 It lets you enable and disable adaptive scalable lgwr, fast log file sync, and log parallelism. Highly experimental, of course! Example 👇
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Hallo @Hosteurope Für was gibt es bei Euch das KIS, wenn Ihr dort sowieso keine geplanten Wartungen mehr ankündigt oder Störungen veröffentlicht?
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Any reason why the OVA image of the Oracle Database Free 23.x Virtual Appliance is not updated anymore? 23.8 is out for quite a time now but the OVA image is still 23.7 (23.7.0.25.01)? Thank you. @GeraldVenzl
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Details about Spectre v2 Mitigations and speculative executions 🤓 blogs.oracle.com/linux/post/…

Understanding Spectre v2 Mitigations on x86

A one stop shop for learning all about Speectre v2 mitigations on x86 architecture.

blogs.oracle.com
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Well 🧐 cloudsek.com/blog/the-bigges…

The Biggest Supply Chain Hack Of 2025: 6M Records Exfiltrated from Oracle Cloud affecting over 140k...

CloudSEK uncovers a major breach targeting Oracle Cloud, with 6 million records exfiltrated via a suspected undisclosed vulnerability. Over 140,000 tenants are impacted, as the attacker demands...

cloudsek.com
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Stefan Koehler retweeted
Christoph Lutz@chris_skyflier
6 Mar 2025
For geeks: two bpftrace scripts to map UTS event and component names to their internal ids. t.ly/bGj0M t.ly/ypKuv Didn’t plan on it, but sometimes the rabbit hole chooses you... Turns out "oradebug doc" doesn't expose all trace events.
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Stefan Koehler retweeted
Tanel Poder 🇺🇦
@TanelPoder
24 Jan 2025
Profile Explorer is a tool for viewing CPU profiling traces collected through the Event Tracing for Windows (ETW) infrastructure on machines with x64 and ARM64 CPUs github.com/microsoft/profile…
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Stefan Koehler retweeted
Christoph Lutz@chris_skyflier
16 Jan 2025
It continues to amaze me time and again what bpf based tracing makes possible … been looking into Oracle write consistency and update restart mechanics recently and tinkered with a bpftrace script to detect restarts system-wide and in real-time: t.ly/MgyQ- 🤓
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Stefan Koehler retweeted
Christoph Lutz@chris_skyflier
7 Jan 2025
1/4 Interesting UPDATE restart variation: Oracle may try to update a row during the ALL LOCKED phase that wasn't returned and locked in the prior LOCK phase (row 0 in the example).
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A visionary leader for a nation, and look at what we got: @Bundeskanzler with his „Sparbuch“ and „debt fantasies“ 🫣
Nayib Bukele
@nayibbukele
11 Nov 2024
I told you so.
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What is this new My Oracle (Cloud) Support Portal? At first I only got errors when accepting the Terms of Use and now the bug database is gone? How can I search the bug database in the new my Oracle (Cloud) Support Portal? All I see is "Knowledge", "Documentation" & Communities
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Ahh I found it. After struggling with all the login errors you have a tiny little link called "Or sign in to other Oracle Support portals" (Support for Oracle Hardware, Software, and Managed Cloud) on the landing page. There you have the good old important information.
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Since a few hours I am going down the CPU scaling governors/drivers rabbit hole - Oh boy this is a mess 😱 Love the term "Autonomous frequency scaling" with Intel CPUs and we all know what this means 😅 Can't set fixed perf mode with active intel_pstate wiki.archlinux.org/title/CPU…
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Hey sweetie - Ghidra with XCOFF loader/support blog.silentsignal.eu/2021/04… It was a little bit messy to get it compiled and running with Ghidra on Kali 2024.3 but we can finally start digging
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Shout out to my Oracle folks The Oracle Messaging Gateway is deprecated according to the Oracle 23ai documentation and TxEventQ is the new way to go. Ok fine, but how to integrate MQ Series with TxEventQ now. Do we need to code our own client/agent for that? 🤔 Thank you 🙏
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I know that there is some sample code here ( github.com/oracle/microservi… ) but that would be a huge step backward if I need to code my own agent for reading data from TEQ and putting into MQ or vice versa.

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Stefan Koehler retweeted
Tanel Poder 🇺🇦
@TanelPoder
15 Aug 2024
I will be speaking at the @ebpfsummit 2024 conference about a new way for approaching Linux system performance, with 0x.tools and eBPF! Free online event on September 11th, 2024 ebpf.io/summit-2024/ See you there!
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