ORA-38760: This database instance failed to turn on flashbac

ORA-38760: This database instance failed to turn on flashback database，ora-38760flashback

ORA-38760: This database instance failed to turn on flashback database

问题背景:
       测试数据库执行shutdown immediate，日志里面报错，错误信息为：ORA-19815: WARNING: db_recovery_file_dest_size of 4322230272 bytes is 99.77% used, and has 9814016 remaining bytes available.
       随即我执行startup force mount将数据库强制关闭并启动到mount状态，通过RMAN把历史备份和归档信息都删除后启动数据库报错ORA-38760.

问题现象：

SQL> startup mount;
ORACLE instance started.

Total System Global Area 2872786944 bytes
Fixed Size                  2256712 bytes
Variable Size            2634023096 bytes
Database Buffers          218103808 bytes
Redo Buffers               18403328 bytes
Database mounted.
SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-38760: This database instance failed to turn on flashback database

问题分析：
    该错误通过查看Metalink 后得知是因为Flash back信息不完整导致。

[oracle@db01 ~]$ oerr or 38760
oerr: Unknown facility 'or'
[oracle@db01 ~]$ oerr ora 38760
38760, 00000, "This database instance failed to turn on flashback database"
// *Cause: Database flashback is on but this instance failed to
//         start generating flashback data. Look in alert log for more
//         specific errors.
// *Action: Correct the error or turn off database flashback.

解决办法：

#1、关闭flash backup再open database
SQL> alter database flashback off;
SQL> alter database open;

#2、另外一种办法直接关闭数据库后再启动也是可以的
SQL> startup force mount;
ORACLE instance started.

Total System Global Area 2872786944 bytes
Fixed Size                  2256712 bytes
Variable Size            2634023096 bytes
Database Buffers          218103808 bytes
Redo Buffers               18403328 bytes
Database mounted.

SQL> alter database open;

Database altered.
SQL>

flashback database要求数据库必须处于归档模式，且闪回之后必须使用resetlogs打开数据库
查看数据库的归档模式及闪回是否启用
SQL> select log_mode,open_mode,flashback_on from v$database;

LOG_MODE OPEN_MODE FLASHBACK_ON
------------ ---------- ------------------
ARCHIVELOG READ WRITE NO --FLASHBACK_ON为NO，则表示闪回特性尚未启用