VMS Help TCPIP Services, TELNET, TN3270 Keyboard Functions, REFR  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    VT100: Ctrl/W               VT200: Ctrl/W or F20
    DEFINE_KEY Function: REFRESH

    Removes TN3270 error messages, operating system messages, or
    other messages that appear on your screen. This key function
    deletes extraneous characters from your screen and redisplays the
    fields and data that were on the screen before the interruption.

    This function does not transmit or receive data from the remote
    host. It is a local OpenVMS function.