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