var db, writeq: shared; rc: integer = 0; ww: integer = 0;

Reader Process

region db when ww = 0
  begin 
    rc = rc + 1 
    read database
    rc = rc - 1 
  end

Writer Process

ww = ww + 1
region db when rc = 0
  begin write database end
ww = ww - 1