hot standby is not possible because max_connections = xx is a lower setting than on the master

postgresql主备高可用版在搭建主备流复制时，备库启动报错：

hot standby is not possible because max_connections = 300 is a lower setting than on the master server (its value was 500)

原因是：顾名思义，备库的max_connections参数值为300，小于主库的主库的max_connections参数值500。也就是说在搭建备库时，备库的max_connections不能小于主库的配置。