Declares an external reference to the SQLCA structure for SQL
    precompiled C programs. If you have multiple modules that use the
    INCLUDE SQLCA statement, you can add the EXTERNAL keyword to all
    but one of them.

    If your application shares the SQLCA among multiple images, one
    image must define the SQLCA while all other images must reference
    the SQLCA. Use the EXTERNAL keyword to reference the SQLCA.