环境：RAC+单机 Dataguard
问题：启动备库到ADG模式时，发现后台归档日志并不同步

1、在备库中发现日志的归档日志不同步，内容如下：
MRP0: Background Media Recovery process shutdown (strac)
Managed Standby Recovery Canceled (strac)
Completed: alter database recover managed standby database cancel
Sun Mar 04 16:35:33 2018
Archived Log entry 96 added for thread 2 sequence 130 ID 0x971d6184 dest 1:
Sun Mar 04 16:35:33 2018
RFS[5]: Selected log 11 for thread 2 sequence 131 dbid -1759711868 branch 947273412
Sun Mar 04 16:35:34 2018
Archived Log entry 97 added for thread 2 sequence 131 ID 0x971d6184 dest 1:
RFS[5]: Selected log 11 for thread 2 sequence 132 dbid -1759711868 branch 947273412
Sun Mar 04 16:35:36 2018
Archived Log entry 98 added for thread 2 sequence 132 ID 0x971d6184 dest 1:
RFS[5]: Selected log 11 for thread 2 sequence 133 dbid -1759711868 branch 947273412
Sun Mar 04 16:39:32 2018

2、当在主库节点1中做切换时，备库中日志并不打印相关的日志进程信息，如果在主库节点2中做日志切换时，备库中是有打印日志的信息内容，内容见第一步中信息

3、通过第二步中的现象描述，可以先大概判断为是主库节点1中DG信息可能有问题导致归档日志无法同步过去

4、查询主库中配置归档位置配置的是否有错误信息，查询的结果如下：
SQL> select error from v$archive_dest where target='STANDBY'
2 ;

ERROR

ORA-12154: TNS:could not resolve the connect identifier specified

SQL> select error from v$archive_dest ;

ERROR

ORA-12154: TNS:could not resolve the connect identifier specified

ERROR

ERROR

TNS Ping Utility for Linux: Version 11.2.0.4.0 - Production on 04-MAR-2018 16:57:32

Copyright (c) 1997, 2013, Oracle. All rights reserved.

Used parameter files:

Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.103)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = strac)))rac =
TNS-12533: TNS:illegal ADDRESS parameters
7、此时在主库节点2中tnsping 备库服务名发现是可以正常解析过来的
[oracle@rac2:/home/oracle]$tnsping strac

TNS Ping Utility for Linux: Version 11.2.0.4.0 - Production on 04-MAR-2018 16:58:17

Copyright (c) 1997, 2013, Oracle. All rights reserved.

Used parameter files:

Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.103)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = strac)))
OK (50 msec)

8、检查主库节点1中的TNS文件配置，经发现主库节点1中的TNS有很多的重复项，从而导致备库不能同步归档日志