在dataguard搭建之后，主库报错：
Tue Jul 31 15:57:11 2018
Error 12154 received logging on to the standby
PING[ARC5]: Heartbeat failed to connect to standby 'dghq'. Error is 12154.
tnsping dghq是ok的。
检查lns进程不存在
SQL> select process, status, thread#,sequence#, block#, blocks from v$managed_standby;
PROCESS STATUS THREAD#SEQUENCE# BLOCK# BLOCKS
------------------ ------------------------ ---------- ---------- ---------- ----------
ARCH CONNECTED 00 0 0
ARCH CLOSING 1 154096 666
ARCH CONNECTED 00 0 0
ARCH CLOSING 1 17 1 400
ARCH CLOSING 1 17 1 400
ARCH CLOSING 1 14 1 24896
ARCH CONNECTED 00 0 0
ARCH CONNECTED 00 0 0
ARCH CONNECTED 00 0 0
ARCH CONNECTED 00 0 0
最后我修改了/etc/hosts后问题解决了--前两行内容注释掉，最后把备库的ip和别名也写到文件里，重启os。
[oracle@oraclerac1 ~]$ more /etc/hosts
#127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
#::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.10.180 oraclerac1
192.168.10.181 oraclerac2
