**oracle数据库切换DG步骤** 备注：应用服务要先停止对外服务 1.先将主库切换成备库，然后将原主库启动到物理库的状态 ``` SQL> Alter database commit to switchover to physical standby with session shutdown; ``` 2.关闭主库 ``` SQL> shutdown immediate; ``` 3.打开数据库nomount ``` SQL> startup nomount; ``` 4.更改主库为备库 ``` SQL> alter database mount standby database; SQL> alter database recover managed standby database disconnect from session; ``` 如果配置了 standby redo log 并需要启用实时同步则执行以下代码 ``` SQL>alter database recover managed standby database using current logfile disconnect from session; ``` 5.将备库切换成主库 ``` SQL> select switchover_status from v$database; SQL> select * from v$version where rownum<2; SQL> alter database commit to switchover to primary with session shutdown; ``` 如果备库还有未应用的日志则执行 ``` SQL>alter database recover managed standby database disconnect from session; SQL> shutdown immediate; SQL> startup; ``` 切换日志进行检查 ``` SQL> select max(sequence#) from v$log; SQL>select sequence#,applied from v$archived_log; SQL> alter system switch logfile; ```