LR Classic has just been upgraded from v10 to v10-v11, and I've just noticed that the lrcat file for the new version is about 19% the size of the previous version (from 8.98 GB down to 1.68 GB). Is this a major upgrade of the file system or do I have a problem? Can I delete the old lrcat file safely?
It sounds like your old catalog had not been optimized for a very long time. How many images does the catalog have? 8.98 GB is extremely large for a catalog file, 1.68 GB is much more what you would expect.
There were about 13000 images most dng. I thought I had optimised the catalogue fairly recently. I'm not too concerned as nothing seems to be missing and I have now added a whole lot more, up to 49,000.