{HEAD ~ controller} means for updating, via non concurrent clock cycles, {TAIL ~ the associated mirror image data validity status information} in said first directory means 
for updating via
{ HEAD ~ controller } means for updating , via non concurrent clock cycles , { TAIL ~ the associated mirror image data validity status information } in said first directory means
HEAD HEAD HEAD HEAD HEAD OTH REL REL OTH REL OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH