In Oracle Forms, messages with a level greater than 25 are considered critical or serious messages that cannot be suppressed by the SUPPRESS_MESSAGE built-in or by the ON-ERROR trigger. This design prevents applications from hiding important errors from users. Level 0 messages are informational, level 1-25 messages can typically be suppressed programmatically, but messages with level 26 or higher bypass suppression mechanisms. "Busy" and "Working" messages are not related to message levels but rather indicate processing state.