LightroomClassic

[KeithG01]

As of yesterday, I cannot open LrC as it says that the catalogue is being used by another program. As far as I can tell it is not being used by another program. Have tried switching on/off etc. Any ideas?

[dj_paige · Accepted solution]

In your operating system, go to the folder where the catalog file is located. In that folder is a file whose name ends with .LOCK (might be lower case). Delete that .LOCK file. DO NOT DELETE ANYTHING ELSE.

[KeithG01]

Thank you, everything back to normal. Could you please explain further i.e. why/when is the .Lock file created?

[johnrellis]

When LR starts, it creates the .lock file, and when it exits normally, it deletes it. The presence of the .lock file indicates that an instance of LR is aleady accessing the catalog, to prevent another instance of LR trying to access it.  If LR exits abnormally (e.g. a crash), then the .lock file will still be there, and you'll have to delete it manually, as explained above.

This is a poorly implemented feature -- there are better ways to implement this technically, but Adobe has never bothered.