FullCalendar is only searching for a range in JSON

What happens is that the calendar is not fetching all the events from the database, it searches only what I'm looking at, it can be the month, week or day, then when I click the NEXT / PREV buttons on the calendar it search the data in mysql again. And it takes so long, how to do it all at once?

events: {
            url: 'events-json-ajax.php',
             cache: true,
            type: 'POST',
              data: {
                room: $('#room option:selected').val(),

              },
            error: function() {
            alert('erro ao tentar carregar os agendamentos');
            },
           success: function(){

            }
        },
        loading: function(bool) {
        $('#loading').toggle(bool);
        },