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

       /NOUSER_ROUTINE

    Specifies that no user routines shall be called at the start and
    end of each system service call. This is the default upon entry
    into the PCA Collector.