Noncoverage plots are typically used to see what portions of your
    program are not covered by your test system. Often, portions of
    your program cannot or should not be tested, or are too difficult
    to test. PCA provides ways to preserve the decisions and analysis
    from run to run of the same image, and from version to version of
    a program.

    The SET ANC command is used to specify which lines or codepaths
    in your program are acceptably not covered. It can be used with a
    program address domain nodespec or in conjunction with traverse
    commands. See SET ANC and Traverse_Commands for more information.

    The PLOT/ANC command will highlight those portions of your
    program that are not covered and have not been specified as
    acceptably not covered. That is, those portions of your program
    for which you want to write tests.

    The MERGE/ANC command is used to bring forward acceptable
    noncoverage points from one version of an image to another. Note
    that when you have modified your program, you cannot append new
    coverage data to the old data file. While some of the acceptably
    noncovered points specified in the old file may not be valid
    because you have changed the program, chances are that most of
    the points are still valid and you would like to preserve them.

    The MERGE/ANC command does just that. It preserves those
    acceptably noncovered points which are still valid for the new
    image. It validates the points on a routine-by-routine basis by
    looking at the codepath information from both images. If all
    the codepaths are at the same offsets from the beginning of
    the routine, then the routine is considered unchanged and any
    acceptably noncovered points within that routine are moved from
    the old version of the data file to the new version.

    The SET COVERAGE/ANC command instructs the Collector to store the
    codepath information required by the MERGE/ANC command.