LRC (almost) hangs (Mac Tahoe; LRC 15.1)

Question

For the past two months or so I have been having huge problems with LRC. At irregular intervals LR would slow down so much that working with it was impossible. Simply clicking a button would result in a delay of up to several minutes. Under these circumstances no editing was possible. I have discussed this at length on The Lightroom Queen forum (https://www.lightroomqueen.com/community/threads/lr-classic-15-0-1-slows-down-dramatically-in-a-session.53969/page-2#posts) and tried numerous suggestions, all to no avail. Now I think I may have found the culprit but rather than solving anything it just exacerbates the problems resulting in a right mess.

I think the problem is with a corrupt lrcat-data file. I came across the following in the LR log file on my Mac Studio (in "big_data_db_retrieve_file.log"):

2026-01-11 10:03:17.9880000+01:00, NotFound:
2026-01-11 10:49:48.0280000+01:00, Error Report
2026-01-11 10:49:48.0280000+01:00, Pixel-Masks DB path : /Users/luukhouwen/Pictures/test/test.lrcat-data
2026-01-11 10:49:48.0280000+01:00, NotFound:
2026-01-11 10:49:48.0340000+01:00, Error Report
2026-01-11 10:49:48.0340000+01:00, Pixel-Masks DB path : /Users/luukhouwen/Pictures/test/test.lrcat-data
2026-01-11 10:49:48.0340000+01:00, NotFound:
2026-01-11 20:10:06.2000000+01:00, Error Report
2026-01-11 20:10:06.2010000+01:00, Pixel-Masks DB path : /Users/luukhouwen/Pictures/test export/test export.lrcat-data
2026-01-11 20:10:06.2010000+01:00, NotFound:
2026-01-11 20:10:06.6630000+01:00, Error Report
2026-01-11 20:10:06.6630000+01:00, Pixel-Masks DB path : /Users/luukhouwen/Pictures/test export/test export.lrcat-data
2026-01-11 20:10:06.6630000+01:00, NotFound:
2026-01-11 20:10:07.0430000+01:00, Error Report
2026-01-11 20:10:07.0430000+01:00, Pixel-Masks DB path : /Users/luukhouwen/Pictures/test export/test export.lrcat-data
2026-01-11 20:10:07.0430000+01:00, NotFound:

Adobe notes on their site (https://helpx.adobe.com/lightroom-classic/kb/catalog-faq-lightroom.html) that one can delete this file but that you get a warning message after starting LR that you will lose all your AI edits. So I tried it and deleted this file. I got the message and continued and lost all my AI edit but LR runs smoothly again (at least for the 20 minutes or so that I tried it). What Adobe doesn‘t say is that all the files that had an AI edit now come up with an error message “An unknown error occurred” and cannot be edited any more (resetting the edit history for example doesn’t work any longer).

So I thought I would go back to a backup in November last when I reorganised my catalog using date folders rather than location folders. This backup appears to work but represents a state of the catalog in which I hadn't completely finished organising it yet. Moreover, I got a new computer in the meantime and can now save the catalog on the internal SSD instead of on an external drive. So I pointed the catalog to the right folder and it shows me lots of folders with question marks because they no longer exist. I recreated some of the new folders and synchronised them. To my surprise I ended up with folders in which the original files are largely missing or not shown, only the jpgs generated within LR are shown. What could be going on and what is the best approach now to minimise my losses?

johnrellis · Accepted Answer

I tried it again and this time it seems to have worked, so ignore the last post. t may have been caused by the fact that after a fresh installation of LR 15.0.1 I had not switched on Auto Sync (well, as a matter of fact I had, but it seems to have switched itself off again).

"I had not switched on Auto Sync"

It's not necessary to use Auto Sync with the workaround steps. I think you were tripping over the bug with the AI Edit Status button that I just described above.

johnrellis · Answer

That help page is incorrect:

Managing AI Edits and Missing .lrcat-data File

If the ‘.lrcat-data’ file is missing or misplaced, images in Lightroom Classic will lose added AI edits permanently if they have AI edits. In such cases, when you open a catalog, Lightroom Classic displays a warning dialog.

In fact, you won't lose AI edits permanently, with one (important) partial exception.

The main catalog file (.lrcat) records all the applied AI edits and their parameters (brush strokes, mask positions, other settings). Whereas the .lrcat-data file records the results of computing the AI commands, e.g. the results of applying Denoise.

If you delete the .lrcat-data file, then you can recompute the exact same AI edits results by starting LR, selecting all the photos in Library, and doing Photo > Develop Settings > Update AI Settings (and potentially waiting a very long time).

The one exception is Generative AI Remove. The brush strokes are recorded in the .lrcat file. But when you do Update AI Settings, the Adobe servers will return different replacement variations for those brush strokes, and in general, there's no way to recover the original variation you had chosen for each remove. Usually, this isn't a big deal, since the variations are all pretty good replacements. But for some harder removes, you may have examined many variations to find the one best one; for such removes, you'll have to reexamine all the variations to make sure you've got good ones. (This is a major design boo boo.)

Managing AI Edits and Missing .lrcat-data File

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