1.查看从库同步是否正常

从库：

SELECT PROCESS,STATUS,THREAD#,SEQUENCE#,BLOCK#,BLOCKS FROM V$MANAGED_STANDBY;

发现MRP0没启动

解决方法：

继续执行：

 >alter database recover managed standby database using current logfile disconnect from session;

 >SELECT PROCESS,BLOCKS FROM V$MANAGED_STANDBY;

 发现还是mrp0没启动

继续执行：

alter database recover managed standby database cancel;
alter database recover managed standby database using current logfile disconnect from session; 

SELECT PROCESS,BLOCKS FROM V$MANAGED_STANDBY;

发现执行第2条报错：

想重启实例mrp0能不能起来？

重启实例：

shutdown immediate;
startup nomount;
alter database mount standby database;
alter database open read only;
alter database recover managed standby database using current logfile disconnect from session;

发现从库出问题了

因为不太懂oracle，重建从库比找原因解决问题快

开始重建从库：

从库执行：

su - oracle

sqlplus  / as sysdba

select open_mode from v$database;  

shutdown immediate
startup nomount    切换到nomount模式

然后到主库开始同步从库：

su - oracle

rman target sys/oracle auxiliary sys/oracl[email protected]

cat $ORACLE_HOME/network/admin/tnsnames.ora