The following example shows how to unset the mask defined for the address field of the Customer table, using the unsetDDMMask() method:
USING OpenEdge.DataAdmin.DataAdminService FROM PROPATH.

DEFINE VARIABLE service AS DataAdminService NO-UNDO. 
DEFINE VARIABLE lResult AS LOGICAL NO-UNDO.

service = NEW DataAdminService(LDBNAME("DICTDB")). 

lResult = service:unsetDDMMask("customer","address").