What is the difference between active file and unlocked file?
The active file is the file that you are working in. It is the only file that can geometry added, modified or deleted. Other attached files in Worksession can be either unlocked or locked. If an attached file is locked then all the layers in the file are locked, and objects in the file cannot be selected. An unlocked file but with all layers locked is the same as a locked file.
What about unlocked file with unlocked layers? Is it the same file as active file?
There is a fundamental difference in Worksession between the active file and other attached files.
Only in the active file can objects be added, modified or deleted. And there can only be one active file.
Objects in other files which are on unlocked layers can be selected for purposes such as measurements, to use as cutting objects in Trim, Split, etc, and any other use which does not modify or delete the object.
Layer locking in Worksession follows the same rules as when working with a single file. When a layer is locked all sub-layers are also locked. And as discussed above when a file in Worksession is locked all layers in that file are locked. It is not possible to lock the active file but layers in the active file can be locked.
All objects in attached files are visible if they are on layers which are turned on, and the objects have not been hidden.
Which file is active can be changed at any time.
All files can be unlocked.
Any file or files other than the active file can be locked.
How Worksession functions may become clearer if you experiment using Worksession with several files.
I believe that Worksession documentation should include these definitions: You are editing active file. Other users are editing locked files. They are not editing unlocked files.
That would be misleading and incorrect. Perhaps you should re-read my posts above.
A single user of Worksession will have one active file, and may or may not have one or more unlocked attached files, and may or may not have one or more locked attached files. The user can only edit the active file. The user can switch which file is the active file.
My understanding is if multiple users are using Worksession with shared files, then each user will have one active file which is not the active file of any other user. Each user may or may not have one or more unlocked attached files, and may or may not have one or more locked attached files. The user can only edit their active file. The other attached files of a user may or may not be active files for other users.
It seems that there is no contradiction between my description of active, locked, and unlocked files, and your description. My main point is that existing documentation is devoid of definitions of these files. In other words: The active file is the file that you are editing. The locked file is the file that someone else is editing. The unlocked file is the file that nobody is editing. To the best of my knowledge, there two ways to lock a file: open the file, or make it active in the worksession.