关于Firebird数据库的备份

请问这样的代码怎么不能备份数据库？
procedure TForm1.FormCreate(Sender: TObject);
var
SourcePath:string;
begin
SourcePath:=ExtractFileDir(Application.exename);
SourcePath:=SourcePath+'\';
Edit1.Text:=SourcePath+'BackupData\'+'PM.fbk';
end;procedure TForm1.Button2Click(Sender: TObject);
begin
SimpleDataSet1.DataSet.CommandText:='backup database PM.FDB to disk='''+Edit1.Text+'''';
end;