Library /sys$common/syshlp/pca$help.hlb PLOT, Data-kind qualifiers, /COVERAGE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Tallies test coverage data along the horizontal axis. Every
    program unit that is covered (executed at least once) gets a
    full-length histogram bar. To use this qualifier, you must have
    collected test coverage or execution counts data with the SET
    COVERAGE or SET COUNTERS command.