The ExAH roster preference is a checkbox that determines if employees will be available for All Hands callouts or not. If the ExAH roster preference is checked then employees who are on the list will not be available for location based callouts including All Hands callouts.
An All Hands callout calls everyone in the selected location or list, regardless of status. When conducting an All Hands callout, you may have employees in some locations that you do not want called. To indicate which employees you do not want called, you can create a roster that contains just those employees and select a roster preference in the roster's administrative page called ExAH, which stands for Exclude from All Hands. With this preference selected, ARCOS® does not call employees on this roster during an All Hands callout.