This command is a special case of CWD, and is included to simplify the implementation of programs for transferring directory trees between operating systems having different syntaxes for naming the parent directory. See Appendix II for further details. This command allows the user to mount a different file system data structure without altering his login or accounting information. Transfer parameters are similarly unchanged. The argument is a pathname specifying a directory or other system dependent file group designator.
All parameters are reset to the default settings and the control connection is left open.
This is identical to the state in which a user finds himself immediately after the control connection is opened. A USER command may be expected to follow. This command terminates a USER and if file transfer is not in progress, the server closes the control connection. If file transfer is in progress, the connection will remain open for result response and the server will then close it. An Internet Encyclopedia 4.1.1.