{HEAD ~ Scanning engine} 310 sends request 315 to direct {TAIL ~ file system access engine} 360 
{ HEAD ~ Scanning engine } 310 sends request 315 to direct { TAIL ~ file system access engine } 360
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH