Library /sys$common/syshlp/pca$help.hlb CANCEL, VCOUNTERS, Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    The CANCEL VCOUNTERS command cancels vector instruction counters
    at the program locations specified by the node specification
    or by the /ALL qualifier. If you first set a vector instruction
    counter at a program location with SET VCOUNTERS and then cancel
    it with CANCEL VCOUNTERS, no execution count is measured at that
    location when the GO command is entered.