Because any program with appropriate privileges can become a VFS server by calling the v_reg() function, VFS servers can be activated in all the ways that a program can be run on MVS™. They may be independent address spaces with their own START cataloged procedure; they can run as batch programs; or they can be shell processes that are run in the background or started through /etc/init. A VFS server can even be a command or program that is invoked directly by a user and run in the foreground of that user's process.

Once a program successfully calls v_reg(), it is registered as a VFS server with z/OS UNIX and dubbed, if it has not already been dubbed. After a server is registered, appropriate privileges are not needed for subsequent v_ functions.

Server registration is not inherited across fork() or spawn().

A VFS server, like any other program, can use the standard file and socket APIs of z/OS UNIX, along with other MVS APIs. The VFS server aspects of the program have to do only with its use of the VFS callable services API.