What is a LOCK file?

Files that contain the .lock file extension are most commonly associated with Microsoft's .NET Framework. The LOCK file format is used to create "locked" copies of a database file.

When a database is already in use and another user tries to open it, a locked copy of the file will be opened instead of the editable copy. This file is saved with the .lock file suffix. This LOCK file prevents the user from making changes to the file while another user is editing it.

The Adobe Lightroom software application also uses the .lock file extension for locked database files.