------主库defer 日志传输
alter system set log_archive_dest_2=defer;
---enable 日志传输：
alter system set log_archive_dest_2=enable；
-----备库(mount)配置 flashback database：
STANDBY DATABASE: Stop redo apply, configure flashback retention,
start flashback database, open the database and start redo apply (Is active DG).
---检查备库是否启用flashback database:
select flashback_on from v$database;
注意这里需要确认下备库打开模式： mount？readonly with apply？
在11g 环境下备库可能启用了 ADG 特性 备库日志处于实时应用，数据库模式为 readonly with apply
这时需要重启数据库到mount状态修改flashback database 模式；
如果备库处于mount 状态，可以先取消日志apply ，直接打开闪回数据库特性；
---取消备库日志应用：
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;
---需要配置一下两个参数来打开flashback database 特性：
ALTER SYSTEM SET db_recover_file_dest=‘/lixora/lixora/lixora/‘;
ALTER SYSTEM SET db_recover_file_dest_size=100G;
ALTER SYSTEM SET DB_FLASHBACK_RETENTION_TARGET=240; ---4hours
ALTER DATABASE FLASHBACK ON;
--手工创建还原点（该步骤没有测试过）：
Creating Restore point in Physical Standby：
CREATE RESTORE POINT before_damage GUARANTEE FLASHBACK DATABASE
-------备库failover to primary db 应急切换步骤：
（注：模拟主库由于故障无法正常switchover，需要执行failover，强制备库->pridb并接管业务）
1.备库：
由于是failover，所以理解主库这时候已经无法正常使用，只需备库切换至pridb
【前提主库还是可用的：可选】查询没有应用的日志：
SELECT THREAD#, LOW_SEQUENCE#, HIGH_SEQUENCE# FROM V$ARCHIVE_GAP;
select distinct thread#,max(sequence#) over(partition by thread#) a from v$archived_log;
该语句取得当前数据库各线程已归档文件最大序号，如果primary 与standby 最大序号不相同，
必须将多出的序号对应的归档文件复制到待转换的standby服务器。
Cp过来并register
ALTER DATABASE REGISTER PHYSICAL LOGFILE ‘filespec1‘
停止应用恢复模式
alter database recover managed standby database finish;
or
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH FORCE;
转换standbydb为primary db
alter database commit to switchover to primary;
重启数据库，恢复正常业务
alter database open；
数据库角色查看：
select open_mode,database_role from v$database;
OPEN_MODE DATABASE_ROLE
---------- ----------------
OPEN PRIMARY
------恢复failover 的备库：
C. Using SQL*PLUS
Step 1 Determine the Standby Became Primary SCN.
Step 2 Flashback the Failed Primary Database.
Step 3 Convert to physical standby database.
Step 4 Restart Redo Transport.
Step 5 Start Redo Apply.
Step 1 Determine the SCN at which the old standby database became the primary database.
SQL> SELECT TO_CHAR(STANDBY_BECAME_PRIMARY_SCN) FROM V$DATABASE;
Step 2 Flashback the Failed Primary Database to SCN standby_became_primary_scn.
SQL> SHUTDOWN IMMEDIATE;
SQL> startup mount
SQL> FLASHBACK DATABASE TO SCN <standby_became_primary_scn of step 1>;
Step 3 Convert the database to a physical standby database and Restart database in mount stage.
SQL> ALTER DATABASE CONVERT TO PHYSICAL STANDBY;
SQL> SHUTDOWN IMMEDIATE;
SQL> STARTUP MOUNT;
Step 4 Restart Redo Transport to the New Physical Standby Database.
1. If you have not set the remote archive destination on current primary then set remote archive destination:
SQL>ALTER SYSTEM SET LOG_ARCHIVE_DEST_2 = ‘SERVICE=lixora VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=lixora‘ SCOPE=BOTH;
2. Enable the destination
SQL>ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_2=ENABLE;
3. Perform a log switch to ensure that standby database begins receiving redo data from the new primary database
SQL> ALTER SYSTEM SWITCH LOGFILE;
SQL> SELECT DEST_ID, STATUS, ERROR FROM V$ARCHIVE_DEST WHERE DEST_ID=2;
--确认日志是否都apply了？
select applied from v$archived_log;
select message from v$dataguard_status;
Step 5 Start Redo Apply.
SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;
Please see also fallowing docu:
TIPS：
Oracle? Data Guard Concepts and Administration
11g Release 2 (11.2)
13.2 Converting a Failed Primary Into a Standby Database Using Flashback Database
