做dataguard，备库rman同步后alter database open read only发现起不来。rman过程并没有报错，启动备库的时候看alter.log有一堆e
sql> alter database open read only;
alter database open read only
*
error at line 1:
ora-10458: standby database requires recovery
ora-01152: file 1 was not restored from a sufficiently old backup
ora-01110: data file 1: '/oracle/oradata/bstyle/system.309.766573511'
alter.log有报错
error 12154 received logging on to the standby
发生背景：
做dataguard，备库rman同步后alter database open read only发现起不来。rman过程并没有报错，启动备库的时候看alter.log有一堆error 12154 received logging on to the standby，再看主库alter.log，，也有一堆error 12154 received logging on to the standby
这说明什么呢，说明archivelog归档到备库的路径是失败的，归档不成功！但是主库sqlplus连备库，或备库连接主库都是正常的！为什么归档不行呢？
sql> select error from v$archive_dest;
error
-----------------------------------------------------------------
ora-12154: tns:could not resolve the connect identifier specified
i could tnsping the standby from production
dataguard中archive_dest_2是用来指向备库的，负责将归档日志传到备库，检查配置参数
注意dest_2中service=这里应该和tnsnames中定义备库的是一样的，如下图。
我这里就是因为设置的不一样导致归档传出过去。改成一样的后一切ok!!!
相关参考:
oracle data guard 重要配置参数
基于同一主机配置 oracle 11g data guard
探索oracle之11g dataguard
oracle data guard （rac+dg) 归档删除策略及脚本
oracle data guard 的角色转换
oracle data guard的日志fal gap问题
oracle 11g data guard error 16143 heartbeat failed to connect to standby 处理方法