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