writing {HEAD ~ the predetermined data} to a log block corresponding to {TAIL ~ a data block} containing the page 
writing { HEAD ~ the predetermined data } to a log block corresponding to { TAIL ~ a data block } containing the page
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH