This is beneficial for database vendors and users {HEAD ~ whose success} relies on {TAIL ~ their systems performance} 
relies on
This is beneficial for database vendors and users { HEAD ~ whose success } relies on { TAIL ~ their systems performance }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL