ah it doesn't work even if I apply a filter

postdata = $('#grid').jqGrid('getGridParam','postData');

$.extend(postdata, { filters:'', searchField: 'error_val', searchOper: 'eq', searchString: '1'});

$('#grid').jqGrid('setGridParam', { search: true, postData: postdata }).trigger(“reloadGrid”,[{ page: 1 }]);

it filter only the records of the pages I've visited.