There is no service provided to unregister with z/OS UNIX. If and when a VFS server's process terminates, z/OS UNIX removes its registration.

A VFS server can, however, release itself from all z/OS UNIX associations by calling undub (BPX1MPC), which also removes its registration as a VFS server.

When z/OS UNIX removes a VFS server's registration, all of the z/OS UNIX resources that are allocated to that VFS server are freed.