If you have ever opened a PMR for a Domino server crash or hang you are familiar with the debug_threadID notes.ini parameter.

For a while now I have enabled this by default on all of my Domino servers, the only real downside is a slightly busier server console, and more information in the console.log. The upside is more information available to support when it’s needed.

In Domino 8.5.3 debug_threadID is now enabled by default, you can still choose to disable it, but I would recommend leaving it enabled.

Technote 1567602:Lotus Domino 8.5.3 ships with Thread ID debug enabled by default