oracle rac与单实例DG切换

1.主库查看状态（RAC库）

SQL> select database_role,switchover_status from v$database; 

DATABASE_ROLE    SWITCHOVER_STATUS
---------------- --------------------
PRIMARY          SESSIONS ACTIVE

SQL> select inst_id,database_role,switchover_status from gv$database;

   INST_ID DATABASE_ROLE    SWITCHOVER_STATUS
---------- ---------------- --------------------
         2 PRIMARY          SESSIONS ACTIVE
         1 PRIMARY          SESSIONS ACTIVE

2.进行切换（任何一个节点执行即可）

SQL> alter database commit to switchover to physical standby with session shutdown;

3.第二步后RAC数据库实例会关闭，把两个实例启动至mount状态

[oracle@rac01 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Thu Apr 16 11:41:54 2020

Copyright (c) 1982, 2013, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup mount;
ORACLE instance started.

Total System Global Area 5344731136 bytes
Fixed Size                  2262656 bytes
Variable Size            1040189824 bytes
Database Buffers         4294967296 bytes
Redo Buffers                7311360 bytes
Database mounted.

[oracle@rac02 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Thu Apr 16 11:42:39 2020

Copyright (c) 1982, 2013, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup nomount;
ORACLE instance started.

Total System Global Area 5344731136 bytes
Fixed Size                  2262656 bytes
Variable Size            1040189824 bytes
Database Buffers         4294967296 bytes
Redo Buffers                7311360 bytes

4.查看RAC库状态

SQL> select open_mode ,database_role from v$database;

OPEN_MODE            DATABASE_ROLE
-------------------- ----------------
MOUNTED              PHYSICAL STANDBY

5.备库（单实例库）查看状态

SQL> select database_role,switchover_status from v$database;

DATABASE_ROLE    SWITCHOVER_STATUS
---------------- --------------------
PHYSICAL STANDBY SESSIONS ACTIVE

6.切换

SQL> alter database commit to switchover to primary with session shutdown ; 

Database altered.

SQL> select database_role,switchover_status from v$database;

DATABASE_ROLE    SWITCHOVER_STATUS
---------------- --------------------
PRIMARY          NOT ALLOWED

SQL> alter database open;

Database altered.

SQL> select database_role,switchover_status from v$database;

DATABASE_ROLE    SWITCHOVER_STATUS
---------------- --------------------
PRIMARY          RESOLVABLE GAP

7.RAC库（此时已是备库）打开数据库并应用日志

SQL> alter database open; 两节点都要执行
SQL> alter database recover managed standby database disconnect; 任何一个节点执行即可

从实际来看，单实例到RAC的DG，RAC只会使用一个实例来进行日志的应用

参考：https://blog.csdn.net/xxzhaobb/article/details/79109155