DataGuard主備庫切換步驟

舊主庫：
SELECT SWITCHOVER_STATUS FROM V$DATABASE;

SWITCHOVER_STATUS
--------------------
TO STANDBY

alter database commit to switchover to standby with session shutdown;

舊備庫，新主庫：
select switchover_status from v$database;

SWITCHOVER_STATUS
--------------------
TO PRIMARY

其他備庫：
select switchover_status from v$database;

SWITCHOVER_STATUS
--------------------
TO PRIMARY

舊備庫，新主庫
alter database commit to switchover to primary with session shutdown;

alter database open;


舊主庫：
shutdown immediate;
startup;
select open_mode from v$database;

OPEN_MODE
--------------------
READ ONLY

ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT;

其他備庫：
都不需要做操作，但是需要提前開啟state和引數配置正確。


確認切換成功：
select database_role,open_mode from v$database;

檢查同步：
select process,sequence#,status from v$managed_standby;
alter system switch logfile;
select max(sequence#) from v$archived_log where applied='YES';