{HEAD ~ Each processor} has its own cache directory and {TAIL ~ image directory} that duplicate each other non atomically 
has
{ HEAD ~ Each processor } has its own cache directory and { TAIL ~ image directory } that duplicate each other non atomically
HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH