Library /sys$common/syshlp/sysmanhelp.hlb PARAMETERS, WRITE, Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    The PARAMETERS WRITE command writes the system parameter values
    and the name of the site-independent startup command procedure
    from the work area to the active system in memory, the current
    system parameter file on disk, or your choice of a parameter
    file. You can write only dynamic parameter values to the active
    system.

    Both the PARAMETERS WRITE ACTIVE and PARAMETERS WRITE CURRENT
    commands send a message to OPCOM to record the event.