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

    PCA data files, also called performance data files, are created
    by the PCA Collector to store the collected data. The data can
    then be read and analyzed by the Analyzer. For more information
    on how performance data files are used in PCA, see HELP entries
    for the SET DATAFILE, SHOW DATAFILE, CANCEL DATAFILE, LIST, and
    MERGE commands.