Library /sys$common/syshlp/dbg$help.hlb DEBUG, CANCEL, SOURCE, Qualifiers, /LATEST  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Cancels the effect of a previous SET SOURCE/LATEST command, which
    specifies a directory search method. In this case, the CANCEL
    SOURCE/LATEST command directs the debugger to return to searching
    for the exact version of the source file from compilation.
    Because /LATEST is the default setting, this qualifier only makes
    sense when used with other qualifiers, for example, /MODULE.