Would it be possible to retrieve some data from a corrupt catalog? I am particularly interested in retrieving album data: which albums have been in existence, and which files did they contain? With 'retrieve' I mean: by some (database?) program external to PSE. Which file in the catalog folder should I open, if possible at all?
First try the solution to create a 'light' copy of the corrupt catalog.
Create a new folder (anywhere) named something like 'My light catalog'.
From the corrupt catalog folder, copy the database file "catalog.pse18db" and copy it inside the "My light catalog' folder.
Double click that database file.
That will hopefully open the organizer with the light catalog. If it opens, you'll recover most of your organization, albums, keywords, captions and ratings, but nothing about face recognition or visual similarity.
Depending on the result, you might also try to keep the shift key pressed while navigating in the catalog manager to the new catalog folder; you might choose 'repair'.
The above solution may work if the corruption does not affect the main database.
I only use an sqlite utility (database4.exe) to have a look at the contents of the catalogs. I very much doubt that you'll be able to extract albums data from corrupt catalogs.
"I tried your suggestion, but got "The catalog could not be opened. An internal programming error occurred".
Then, it's the main database which is corrupt, which is not common. An external SQL tool may offer a tool to repair the database; I don't know if the 'repair' option in the catalog manager uses that function.
If you have a recent copy of the 'catalog.pse18db' database file, you might try the above 'light catalog' solution. Remember that if what you have is a recent backup folder, it contains a renamed copy 'catalog.buc' of the database. you can rename it back to 'catalog.pse18db'.