When you launch Lightroom, you encounter the error "The Lightroom catalog cannot be opened because another application already has it opened."
When Lightroom is running with a catalog open, it creates a [yourcatalogname].lrcat.lock file next to the [yourcatalogname].lrcat file. This file ensures that there is no other access to the catalog in use. When you exit Lightroom, the lock file is deleted automatically.
However, if Lightroom is not shut down properly, the .lrcat.lock file remains in the same folder as the .lrcat file, which prevents Lightroom from opening.
To resolve this issue, do the following:
- Close the Lightroom application.
- Go to the folder where your catalog file [yourcatalogname].lrcat is saved. By default, Lightroom saves catalogs in the following folders:
- Windows: \Users\[user name]\Pictures\Lightroom
- Mac OS: /Users/[user name]/Pictures/Lightroom
- Move the [yourcatalogname].lrcat.lock file to the Trash (Mac OS) or Recycle Bin (Windows), if it is present at this folder location.
Caution: Do not delete or move the main [yourcatalogname].lrcat file.
- Relaunch Lightroom.
- If your catalog opens successfully, you can empty the Trash (Mac OS) or Recycle Bin (Windows).