This setting is for users on a network to specify whether and how to lock files that are in use.
Locking provides write access for the first person that opens the file. Anyone else who opens the file can read it but is denied write access until the first person closes the file.
An image file is locked when AutoCAD Raster Design toolset creates a lock file using the image base name with a .l_k extension. The lock file is stored in the same directory as the image file or in the lock file directory if you specify one. When you insert an image, AutoCAD Raster Design toolset searches the image directory (or the lock file directory) to see if a lock file already exists for that image. If a lock file exists, then you are prompted that the file is read-only.
If you store lock files in a lock file directory, all raster image files with the same base name as the inserted image are locked. For example, if you insert tutor.rlc, a tutor.l_k file is created in the lock directory. This locks the image that you inserted and any other files with the base name “tutor.”in any directory.
If you do not specify a lock file directory, the lock file is created in the directory where the image is saved. In this case, a lock file locks only images in that directory with the same base name.