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

    You can compare more than one kind of data in the same plot. For
    example, you can plot PC sampling data, page fault data, and I/O
    service calls in the same histogram. This way, you can easily see
    if the PC sampling spikes are caused by page faults or I/O system
    service calls.

    See INCLUDE and EXCLUDE for more information about how to build
    multiple data kind plots.