查看oracle主备日志应用情况：

SQL> select to_char(max(FIRST_TIME),'HH24:MI:SS, yyyy-mm-dd') first_time from v$archived_log where applied='YES';

FIRST_TIME

--------------------

20:57:52, 2018-07-22

在DG上操作：
SQL> select RECOVERY_MODE from v$archive_dest_status where rownum<5;
RECOVERY_MODE
-----------------------
MANAGED
IDLE
IDLE
IDLE

当前没有实时应用
SQL> select group#,member from v$logfile order by 1;


    GROUP#
----------
MEMBER
--------------------------------------------------------------------------------
         1
/oracle/oradata/standby01.log


         2
/oracle/oradata/standby02.log


         3
/oracle/oradata/standby03.log
有standby.log
SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT FROM SESSION;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT FROM SESSION
*
ERROR at line 1:
ORA-01153: an incompatible media recovery is active

需要先断开日志同步：


SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL; 
Database altered.


SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT FROM SESSION;
Database altered.

可以了。
SQL> select RECOVERY_MODE from v$archive_dest_status where rownum<5;


RECOVERY_MODE
-----------------------
MANAGED REAL TIME APPLY
IDLE
IDLE
IDLE