闪回的开启与关闭

（****使用闪回技术、首先要设置闪回恢复区）
设置快速恢复区的地址
SQL> alter system set db_recovery_file_dest='/u01/app/oracle/'scope=both;

System altered.

SQL>
设置快速恢复区的大小

SQL> alter system set db_recovery_file_dest_size=4G scope=both;

System altered
查看快速恢复区的状态
SQL> show parameter db_recovery_file_dest

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest                string      /u01/app/oracle/
db_recovery_file_dest_size           big integer 4G
SQL>

{必须在归档模式下、而且关闭和开启数据库是在mount状态下}
SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            /u01/app/oracle/product/11.2.0/dbhome_1/dbs/arch
Oldest online log sequence     12
Next log sequence to archive   14
Current log sequence           14
查看数据库的闪回是否开启
SQL> select flashback_on from V$database;

FLASHBACK_ON
------------------
NO

SQL>
首先要开启数据库闪回
（1）要在mount状态下
SQL> alter database flashback on;

Database altered.

SQL>
启动到open下
SQL> alter database open;

Database altered.
查看闪回状态
SQL> select flashback_on from v$database;

FLASHBACK_ON
------------------
YES

SQL>
关闭闪回
（1）先关闭数据库 启动到mount状态
SQL> shutdown immediate

Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> SQL>        
SQL> startup mount
ORACLE instance started.

Total System Global Area  835104768 bytes
Fixed Size                  2257840 bytes
Variable Size             541068368 bytes
Database Buffers          289406976 bytes
Redo Buffers                2371584 bytes
Database mounted.
（2)关闭数据库闪回
SQL> alter database  flashback off;

Database altered.
（3）数据库open
SQL> alter database open;

Database altered.
(4)查看数据库闪回状态

SQL> select flashback_on from v$database;

FLASHBACK_ON
------------------
NO