一：问题描述

SQL> alter database flashback on;
alter database flashback on
*
ERROR at line 1:
ORA-38706: Cannot turn on FLASHBACK DATABASE logging.
ORA-38709: Recovery Area is not enabled.

二：出错原因

没有设置闪回恢复区路径

如图：

三：解决办法

设置闪回恢复区路径

SQL> alter system set db_recovery_file_dest='/home/oracle/db_recovery_file_dest';--这里可以自定义路径

System altered.

SQL> show parameter db_recovery;

NAME???????? TYPE? VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest?????? string? /home/oracle/db_recovery_file_
?????? dest
db_recovery_file_dest_size????? big integer 2G
SQL> alter database flashback on;

Database altered.

--没有再报错了