The users element must appear at the beginning and end of the list of Teradata Database users that are affected by the filters defined in the document. You can add user names to the list, each with a separate users element, however, the users element does have to contain individual users. If you do not specify any user elements as children of the users element, the filter applies to all users. See Applying a Filter to All Users.
The users element must appear as a child of a system element. The XML document can contain as many users elements as needed, but only one appearance is typical.