ORA-38706: Cannot turn on FLASHBACK DATABASE logging.

报错：ORA-38706和ORA-38714

步骤如下：

SQL> archive log list

Database log mode              Archive Mode

Automatic archival             Enabled

Archive destination            use_recovery_file_dest

Oldest online log sequence     7

Next log sequence to archive   9

Current log sequence           9

SQL> select log_mode,flashback_on from v$database;

LOG_MODE     FLASHBACK_ON

------------ ------------------

ARCHIVELOG   NO

如果没有开启归档，必须在mount状态下执行：

SQL> alter database archivelog;

否则是无法开启flashback的，因为闪回需要归档

SQL> select open_mode from v$database;

OPEN_MODE
----------
MOUNTED

SQL> alter database flashback on;
alter database flashback on
*
ERROR at line 1:
ORA-38706: Cannot turn on FLASHBACK DATABASE logging.
ORA-38714: Instance recovery required.

在网上google了一下，没找到什么有用的信息，别人出现这个情况是因为归档没有开启，但是我已经开启归档了

查看alert.log文件，也没什么信息，只报了一条：

Wed Aug 21 00:15:20 2013

alter database flashback on

ORA-38706 signalled during: alter database flashback on...

根据提示，理解为需要recover database

SQL> recover database;
Media recovery complete.
SQL> alter database flashback on;
alter database flashback on
*
ERROR at line 1:
ORA-38706: Cannot turn on FLASHBACK DATABASE logging.
ORA-38714: Instance recovery required.

仍然不行，于是从错误代码编号着手，看看有什么有价值的信息

[oracle@RHEL5U3 ~]$ oerr ora 38706

38706, 00000, "Cannot turn on FLASHBACK DATABASE logging."

// *Cause:  An ALTER DATABASE FLASHBACK ON command failed.

//          Other messages in the alert log describe the problem.

// *Action: Fix the problem and retry.

这个等于没说，alert.log里没有什么内容

[oracle@RHEL5U3 ~]$ oerr ora 38714

38714, 00000, "Instance recovery required."

// *Cause:  An ALTER DATABASE FLASHBACK ON command failed because the 

//          database either crashed or was shutdown with the ABORT

//          option.

// *Action: Open the database and then enter the SHUTDOWN command with the

//          NORMAL or IMMEDIATE option.

哇，亮点来了，看到没有，cause里写得很清楚，由于数据库crash或shutdown abort

action也写明了解决方法，只要open以后，再正常关闭数据库就行了，多简单

SQL> alter database open;

Database altered.

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

Total System Global Area  285212672 bytes
Fixed Size                  1218992 bytes
Variable Size              67110480 bytes
Database Buffers          213909504 bytes
Redo Buffers                2973696 bytes
Database mounted.
SQL> alter database flashback on;

Database altered.

flashback开启成功，验证一下：

SQL> select log_mode,flashback_on from v$database;

LOG_MODE     FLASHBACK_ON

------------ ------------------

ARCHIVELOG   YES

总结：出现错误要根据错误提示去一步步解决问题，首先当然是查看alert.log，看是否存在有价值的提示，如果没有，那么就要从ORA-xxxxx 错误本身来查找问题了，如果google不到好的解决方案也不要气馁，我们还有oracle提供的oerr命令，非常之好用，有时候使用它会给你带来意外惊喜哦