The datum feature symbol should be shown attached to the datum feature in at least one view. Then, if it is desired to identify the datum (or datum feature) in additional views the datum feature symbol may be repeated if the datum feature exists in the view. If the view doesn't include the datum feature, a centerline that represents the datum may be labeled using a leader line and a note such as " DATUM A" (or whatever letter is appropriate). I do not recommend attaching the datum symbol to the centerline of the datum feature.