今天搭建单实例+备库（rac），备库节一已同步正常，准备启动实例二，报错了
查看节点二的alert 告警日志，发现304 错误，是不是我的instance_number ,查看参数文件，发现 instance_number 没有设置，
修改后再次启动实例二 ，正常启动
starting up 1 shared server(s) ...
Thu Sep 27 11:47:01 2018
USER (ospid: 28763): terminating the instance due to error 304
Instance terminated by USER, pid = 28763
Fri Sep 28 15:36:04 2018
Starting ORACLE instance (normal)
LICENSE_MAX_SESSION = 0
LICENSE_SESSIONS_WARNING = 0
Initial number of CPU is 40[[email protected] ~]$ oerr ora 304
00304, 00000, "requested INSTANCE_NUMBER is busy"
// *Cause: An instance tried to start by using a value of the
// initialization parameter INSTANCE_NUMBER that is already in use.
// *Action: Either
// a) specify another INSTANCE_NUMBER,
// b) shut down the running instance with this number
// c) wait for instance recovery to complete on the instance with
// this number.