I recently moved Lightroom, including catalog, to my new Dell XPS 8950 system. It seemed to function well, until I made what I thought was an unrelated modification to my system. That modification was to disable Microsoft OneDrive, since I did not want this sitting in memory and absorbing resources. I knew I could always reestablish it, if I changed my mind. I have other cloud services that I prefer.
Then the adventure started. Suddenly, I got a cryptic “Assertion Failed” error message when starting Lightroom. I did a search in Adobe Support on that error and found an interesting entry. As part of the diagnostic procedure was the suggestion to dive into the Windows Registry and see what’s there. This must be done with great care, since you are digging around in the “heart and soul” of the system. I followed the steps carefully and was surprised to find that my Lightroom catalog files were not in the usual /username/Pictures location. Rather, it was /username/OneDrive/Pictures. Now, I know for sure that I never specified OneDrive as a storage location, so that can only mean that Microsoft, in their zeal, had set that up as a default when Windows was installed. I had some strong, not very Christian comments about this “feature.”
I immediately moved the whole catalog file to its proper place on the C-drive, double-clicked on the Lightroom catalog #xxxx.lrcat file and Lightroom started and automatically assigned the catalog to the new, proper location. Problem solved.
Let me also note that I realize there are users who intentionally use OneDrive to store their catalog. Putting the catalog in the cloud has advantages when you are using Lightroom on multiple platforms. That’s fine, as long as extra care is being used to keep current backups locally on a different storage medium.