1.确认数据库是否开启Flashback Database功能
若未开启，则继续，若已经开启，请从此小文儿飘过~~
SYS@ora11g> select flashback_on from v$database;
FLASHBACK_ON
------------------
NO
2.修改db_recovery_file_dest、db_recovery_file_dest_size及db_flashback_retention_target三个参数内容
1）db_recovery_file_dest、db_recovery_file_dest_size两个参数用于指定闪回日志存放位置及最大大小。可以根据具体环境做相应调整。
SYS@ora11g> show parameter recovery_file
NAME TYPE VALUE
-------------------------- ----------- ------------------------------
db_recovery_file_dest string /u01/app/oracle/flash_recovery
_area
db_recovery_file_dest_size big integer 3852M
2）确认db_flashback_retention_target参数设置的内容。
db_flashback_retention_target参数限定了闪回可恢复的时间范围，默认是1440分钟，一天的时间。
SYS@ora11g> show parameter db_flashback_retention_target
NAME TYPE VALUE
------------------------------------ ----------- ---------
db_flashback_retention_target integer 1440
3.重启数据库到mount状态
SYS@ora11g> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SYS@ora11g> startup mount;
ORACLE instance started.
Total System Global Area 313860096 bytes
Fixed Size 1336232 bytes
Variable Size 239078488 bytes
Database Buffers 67108864 bytes
Redo Buffers 6336512 bytes
Database mounted.
4.在mount状态下启用Flashback功能
SYS@ora11g> alter database flashback on;
alter database flashback on
*
ERROR at line 1:
ORA-38706: Cannot turn on FLASHBACK DATABASE logging.
ORA-38707: Media recovery is not enabled.
此处报错是由于数据库未运行在归档模式，启用闪回数据库功能的前提是数据库运行在归档模式下。因此需要先调整数据库为归档模式。
SYS@ora11g> alter database archivelog;
Database altered.
SYS@ora11g> alter database flashback on;
Database altered.
闪回数据库开启成功。
5.打开数据库
SYS@ora11g> alter database open;
Database altered.
6.验证Flashback功能已经成功开启
SYS@ora11g> select flashback_on from v$database;
FLASHBACK_ON
------------------
YES
7.小结
启用闪回数据库的过程相对简单，注意先保证数据库运行在归档模式下。这是使用闪回数据库的前提，需要熟练掌握。
****************************************************************************************************
闪回区满:
OS: rm -rf [archivelog autobackup backupset controlfile flashback onlinelog]
eg :
archivelog autobackup backupset controlfile flashback onlinelog
[Oracle@jibo PROD]$ cd autobackup/
[oracle@jibo autobackup]$ ls
2014_10_13 2014_10_15 2014_10_16
[oracle@jibo autobackup]$ rm -rf 2014_10_13
[oracle@jibo autobackup]$ rm -rf 2014_10_15
RMAN:
RMAN> crosscheck backup;
RMAN> delete expired backup;
RMAN> crosscheck archivelog all;
RMAN> delete expired archivelog all;
sqlplus：
SYS@PROD>show parameter db_re
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest string /u01/app/oracle/fast_recovery_
area
db_recovery_file_dest_size big integer 4G
db_recycle_cache_size big integer 0
SYS@PROD>desc v$recovery_area_usage;
Name Null? Type
----------------------------------------- -------- ----------------------------
FILE_TYPE VARCHAR2(20)
PERCENT_SPACE_USED NUMBER
PERCENT_SPACE_RECLAIMABLE NUMBER
NUMBER_OF_FILES NUMBER
SYS@PROD>select sum(PERCENT_SPACE_USED) from v$recovery_area_usage;
SUM(PERCENT_SPACE_USED)
-----------------------
33.45
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