开启数据库闪回功能

1、闪回功能必须，设置数据库为归档
SQL> select log_mode from v$database;

LOG_MODE
------------------------
NOARCHIVELOG
SQL> shutdown immediate;
SQL> startup mount;
设置闪回区位置和大小
SQL> show parameter db_recovery

NAME                                 TYPE          VALUE
----------                          ---------       -----------
db_recovery_file_dest                string          +ORAARCH
db_recovery_file_dest_size           big integer      2G
SQL> alter system set db_recovery_file_dest_size=4G;
NAME                                 TYPE          VALUE
----------                          ---------       -----------
db_recovery_file_dest_size           big integer      4G
SQL> alter database archivelog;
SQL> alter database open;

2、设置闪回保留目标时间，默认是一天（和db_recovery_file_dest_size设置有关）单位是秒
SQL>    show parameter retention_target

NAME                                 TYPE                   VALUE
------------------------------------ ---------------------- ------------------------------
db_flashback_retention_target        integer                1440

3、开启闪回功能
SQL> shutdown immediate  
SQL> alter database flashback on;
SQL> alter database open;
SQL> select flashback_on from v$database;

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

4、查看闪回相关视图
SQL> select retention_target,flashback_size,oldest_flashback_time from v$flashback_database_log;

RETENTION_TARGET FLASHBACK_SIZE OLDEST_FLASHBA
---------------- -------------- --------------
            1440        8192000 22-9月 -15
查看开启闪回付出的代价单位字节
SQL> select end_time,flashback_data,db_data,redo_data from v$flashback_database_stat;

END_TIME       FLASHBACK_DATA    DB_DATA  REDO_DATA
-------------- -------------- ---------- ----------
22-9月 -15               8192          0          0

 

 

开启flashback功能后OS回多一个rvwr进程
[oracle@localhost ~]$ ps -ef|grep rvwr
oracle   30058     1  0 20:01 ?        00:00:00 ora_rvwr_mydb