需要的步骤
确保数据库处于归档日志模式：Select log_mode from v$database;
创建闪回恢复区
Alter system set db_recovery_file_dest=‘flash_recover_area’;
Alter system set db_recovery_dest_size=8g;
设置闪回保留目标时间：Alter system set db_flashback_rectention_target=240;
干净的关闭并加载数据库：Shutdown immediate; startup mount;
启用闪回日志记录：Alter database flashback on;
打开数据库：Alter database open;
