The DEMAND statement identifies the SAS variable in the ARCDATA= data set that contains the demand at the node named in the corresponding HEADNODE list variable. The DEMAND list variable must have numeric values. It is not necessary to have a DEMAND statement if the name of this SAS variable is _DEMAND_. See the section Missing S Supply and Missing D Demand Values for cases when the SUPDEM list variable values can have other values. There should be no DEMAND statement if you are solving an LP.