生产上要做灾备系统的应急切换演练，灾备端是由OGG搭建的。由于生产库都比较大10多T，不想演练后重新初始化灾备库，生产库版本为10.2.0.4，于是想到10g的新特性flashback database。演练开始前记录一个还原点，演练结束后闪回到这个还原点，重新同步ogg即可。
测试闪加数据库。
一、开启FLASHBACK DATABASE
数据库版本：10.2.0.4
启用FLASHBACK DATABASE数据库必须为ARCHIVELOG模式，还需要有一个闪回恢复区用于存储闪回日志，RAC中闪回恢复区必须在集群文件系统或ASM中。
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--数据库已开启归档，但还未启用FLASHBACK
SQL>
select
flashback_on,log_mode
from
v$
database
;
FLASHBACK_ON LOG_MODE
------------------------------------------------------ ------------------------------------
NO
ARCHIVELOG
--调整参数
SQL>
alter
system
set
db_recovery_file_dest_size=3G scope=spfile;
System altered.
SQL>
alter
system
set
db_recovery_file_dest=
'/u01/app/oracle/flashback_area/'
scope=spfile;
System altered.
SQL>
alter
system
set
db_flashback_retention_target=2880 scope=spfile;
System altered.
--关闭数据库
SQL> shutdown immediate;
Database
closed.
Database
dismounted.
ORACLE instance shut down.
--启动到mount状态，开启FLASHBACK
SQL> startup mount;
ORACLE instance started.
Total System
Global
Area 599785472 bytes
Fixed
Size
2085776 bytes
Variable
Size
192941168 bytes
Database
Buffers 398458880 bytes
Redo Buffers 6299648 bytes
Database
mounted.
SQL>
alter
database
flashback
on
;
Database
altered.
--启动数据库
SQL>
alter
database
open
;
Database
altered.
--查看新状态
SQL>
select
flashback_on,log_mode
from
v$
database
;
FLASHBACK_ON LOG_MODE
------------------------------------------------------ ------------------------------------
YES ARCHIVELOG
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官方文档：http://docs.oracle.com/cd/B19306_01/backup.102/b14192/rpfbdb003.htm#sthref509
db_recovery_file_dest_size参数表示闪回恢复区的大小
db_recovery_file_dest参数表示闪回恢复区目录
db_flashback_retention_target表是闪回日志保留的时间，单位为分，默认1440(1天)
查看闪回恢复区里已生成闪回日志
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[oracle@rhel5 flashback_area]$ cd /u01/app/oracle/flashback_area/MYDB/flashback/
[oracle@rhel5 flashback]$ ls -l
total 8020
-rw-r
----- 1 oracle oinstall 8200192 Jan 9 14:48 o1_mf_d76cxc1r_.flb
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二、创建测试表
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SQL> conn zx/zx
Connected.
SQL>
create
table
flash_t
as
select
*
from
all_tables;
Table
created.
SQL>
insert
into
flash_t
select
*
from
flash_t;
1559
rows
created.
SQL> /
3118
rows
created.
SQL>
commit
;
Commit
complete.
SQL>
select
count
(*)
from
flash_t;
COUNT
(*)
----------
6236
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三、查看数据库可以闪回的时间点
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SQL>
select
*
from
V$FLASHBACK_DATABASE_LOG;
OLDEST_FLASHBACK_SCN OLDEST_FLASHBACK_ RETENTION_TARGET FLASHBACK_SIZE ESTIMATED_FLASHBACK_SIZE
-------------------- ----------------- ---------------- -------------- ------------------------
7762668 20170109 14:37:32 2880 14467072 590954496
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四、测试闪回数据库到一个时间点
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--记录当前SCN用于闪回数据库
SQL>
SELECT
CURRENT_SCN
FROM
V$
DATABASE
;
CURRENT_SCN
-----------
7765990
--删除测试表
SQL> conn /
as
sysdba
Connected.
SQL>
select
count
(*)
from
zx.flash_t;
COUNT
(*)
----------
6236
SQL>
drop
table
zx.flash_t;
Table
dropped.
SQL>
select
count
(*)
from
zx.flash_t;
select
count
(*)
from
zx.flash_t
*
ERROR
at
line 1:
ORA-00942:
table
or
view
does
not
exist
--闪回数据库
SQL> shutdown immediate;
Database
closed.
Database
dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.
Total System
Global
Area 599785472 bytes
Fixed
Size
2085776 bytes
Variable
Size
192941168 bytes
Database
Buffers 398458880 bytes
Redo Buffers 6299648 bytes
Database
mounted.
--执行闪回
SQL> flashback
database
to
scn 7765990;
Flashback complete.
--以resetlogs方式打开数据库
SQL>
alter
database
open
resetlogs;
--可以使用alter database open read only打开数据库查看闪回后数据库的状态，如果闪回的不理想，重启到mount模式重新做flashback database
Database
altered.
--验证测试表得到恢复
SQL>
select
count
(*)
from
zx.flash_t;
COUNT
(*)
----------
6236
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闪回还可以指定时间或还原点
FLASHBACK DATABASE TO RESTORE POINT BEFORE_CHANGES;
FLASHBACK DATABASE TO TIME "TO_DATE('09/20/00','MM/DD/YY')";官方文档：http://docs.oracle.com/cd/B19306_01/backup.102/b14192/flashptr005.htm#BGBDCAFA
本文转自hbxztc 51CTO博客，原文链接：http://blog.51cto.com/hbxztc/1890433，如需转载请自行联系原作者
