oracle开启闪回

alter system set db_recovery_file_dest='/u01/app/oracle/fast_recovery_area' scope=both; ##闪回文件存放位置
alter system set db_recovery_file_dest_size=8G scope=both;        ##闪回区大小
alter system set db_flashback_retention_target = 1440 scope=both; ##分钟
alter database flashback on;