Lightroom Classic 9.2 Catalog Update Issue - Not Showing PREVIEWS

[jazzrazz]

I recently opened an old Lightroom Catalog on my laptop. (I am away from home and do not have my hard drive with the photos originals on them.) Usually I can open the catalog with no problem and see all the previews/smart previews. The catalog updated itself and the preview files are there (.previews.lrdata) but Lightroom is not reading them. I can't see anything but grey boxes. I am using a macOs Mojave on a Powerbook Pro. I noticed that a couple of new files that I have never seen were also created: lrcat-wal and lrcat-lock. What are these? And, is there anything that I can do to see the previews to edit? I cannot return home due to the pandemic for a while to remake the previews from the original photos. Thank you for any help. 

[John Waller]

Moved from Using The Community forum.

[ManiacJoe]

What version of Lightroom as the old version?

What version of Lightroom is the new version?

The new version 10.x seems smart enough to transfer over the previews during the data migration from an older version. Version 9.x and earlier did not do that. (However, you could do that manually by renaming the old preview folder.)

[JohanElzenga]

The latter is not true. Earlier versions also renamed the previews.lrdata, but it's always possible that something went wrong with that. So first check that the previews have the correct name, which should be {catalogname} previews.lrdata. If not, then renaming them in the Finder should do the trick. It's also possible that there was some corruption in the previews (there is a database inside the previews package). In that case they'll need to be rebuilt and Lightroom can only do that if it has the originals (or smart previews).

The lrcat-wal file is a 'write ahead' file for the catalog. Lightroom stores temporary data in it, that are not yet incorporated in the main catalog. Don't touch it. The lrcat-lock file is a temporary file that Lightroom creates when it is running and deletes when it quits. It's a 'do not touch this database' warning for other apps, to stop another app from trying to open the catalog when Lightroom already has it open (which would corrupt the catalog). Both have nothing to do with you not seeing the thumbnails.

[jazzrazz]

Thank you for your responses. 

I updated to the newest LrC, went back to a previous copy of the catalog and opened it in LrC 10.1.1 and magically it all worked. The previews were all showing. Thank you for your responses. It is helpful to know what the lrcat-wal and lrcat-lock are as well.