PLM check-in/check-out, file

If a user wants to make changes to a unreleased file in the PLM system's file repository (library), the file is checked out and which prevents other users from also modifying the same file. Checking out the file is actually a two-step process: the system first copies the file to the user's computer, and then locks the file from further checkouts (other users can still copy the file). When the file is checked back into the library, the updated file is (1) copied from the user's computer back to the library, and (2) unlocked for other users to check out again. If a user decides not to return a checked-out file, it still must be unlocked. In this case, the PLM system does not copy the file from the user's workspace, but simply unlocks the library file. Once the item associated with the file has been released, the file is locked from further modifications and cannot be checked out, but only copied for use or as the basis for a new item iteration.