A dataset including {HEAD ~ data elements} and order keys for indicating an ordering of {TAIL ~ the data elements} is stored 
A dataset including { HEAD ~ data elements } and order keys for indicating an ordering of { TAIL ~ the data elements } is stored
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH