Section 315. Recording books

Different sets of books must be provided by
  the recording officer of each county, for the  recording  of  deeds  and
  mortgages; in one of which sets he must record all conveyances and other
  instruments absolute in their terms, which are not intended as mortgages
  or  securities  in  the nature of mortgages, and all executory contracts
  for the sale, purchase  or  exchange  of  real  property,  or  memoranda
  thereof,  and  all  instruments  canceling  or extending such contracts,
  which conveyances,  contracts  or  instruments  are  delivered  to  him,
  pursuant  to  law,  to  be  so  recorded,  and  all  forms pertaining to
  commitments of land to continued agricultural production required to  be
  so recorded pursuant to section three hundred six of the agriculture and
  markets  law;  and  in the other set, such mortgages and securities, and
  assignments of rent, delivered to him; excepting that if  the  recording
  is  by  microphotography  or  other  photographic process, the recording
  officer shall not be required to maintain books for  such  records,  but
  shall  provide  such  filing  equipment  as he may deem appropriate. The
  recording officer may, in his discretion, record  in  consecutive  order
  the  instruments received by him, and shall not be required to segregate
  mortgages from deeds or other classes of instruments.