In the Collector, the SET DATAFILE command identifies the
    performance data file the Collector should use to record symbol
    information and performance or coverage data. No performance or
    coverage data is actually written to the specified file until you
    enter the GO command. You can thus respecify the data file with
    another SET DATAFILE command if you need to correct the data file
    specification.

    If you want to append the data from the present collection run to
    an existing performance data file, use the /APPEND qualifier. If
    you want to measure the performance of a shareable image, use the
    /SHAREABLE qualifier.

    In the Analyzer, the SET DATAFILE command identifies a
    performance data file to be processed by the Analyzer. Data from
    this file is used by all subsequent PLOT, TABULATE, LIST, and
    SHOW commands. You can use the SET DATAFILE command to change the
    performance data file any number of times during the Analyzer
    session. The Collector builds the performance data file to
    contain all symbol information and all performance or coverage
    data required by the Analyzer.