SWITCHOVER_STATUS
--------------------
TO LOGICAL STANDBY
此次检查结果关系到switchover转换是否能够成功。
8.把当前的Primary转换成逻辑Standby
SQL> alter database commit to switchover to logical standby;

Database altered.
9.逻辑Standby在接收到前Primary的转换消息，并完成相关的REDO数据之后，会自动暂停ＳＱＬ应用。如果之前没有启动ＲＥＤＯ应用，现在启动还不晚。
SQL> alter database start logical standby apply;

Database altered.

SQL> select switchover_status from v$database;

SWITCHOVER_STATUS
--------------------
PREPARING SWITCHOVER 等会……

SQL> select switchover_status from v$database;

SWITCHOVER_STATUS
--------------------
TO PRIMARY
10.转换逻辑Ｓｔａｎｄｂｙ为新的Ｐｒｉｍａｒｙ数据库
SQL> alter database commit to switchover to primary;

Database altered.
启动新的逻辑Ｓｔａｎｄｂｙ（之前的Ｐｒｉｍａｒｙ）ＳＱＬ应用
SQL> alter database start logical standby apply immediate;

Database altered.
测试：
在新的Prｉｍａｒｙ里面插入测试数据：
SQL> select * from scott.test;

ID
----------
1
2
3

SQL> insert into scott.test values(4);

1 row created.

SQL> commit;

Commit complete.

检查新的standby：
SQL> select * from scott.test;

ID
----------
1
2
3

SQL> select * from scott.test;

ID
----------
1
2
3

SQL> select * from scott.test;

ID
----------
1
2
3
可能会延迟……
SQL> select * from scott.test;

ID
----------
1
2
3
4
逻辑Ｓｔａｎｄｂｙ角色转换成功……