Syntax options:

    username | DEFAULT

    Specifies the operating system user name that the database system
    uses for privilege checking.

    You can specify a character string literal for the user name or
    you can specify the DEFAULT keyword. The DEFAULT keyword allows
    you to avoid placing the user name in a program's source code.
    If you specify the DEFAULT keyword, you pass the user name to the
    program by using a command line qualifier when you compile an SQL
    module or precompiled program. You use the USERNAME qualifier.