For example, {HEAD ~ web servers} continue to request operations on {TAIL ~ the database} while content is being moved 
For example , { HEAD ~ web servers } continue to request operations on { TAIL ~ the database } while content is being moved
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH