取消快速恢复区报错ORA-38775，如下为实际操作过程：

SQL> show parameter db_recovery_file_dest

NAME                                 TYPE                   VALUE

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

db_recovery_file_dest                string                 /u01/app/oracle/oradata/orcl151/flashback

db_recovery_file_dest_size           big integer            6G

SQL> alter system set db_recovery_file_dest='';

alter system set db_recovery_file_dest=''

*

ERROR at line 1:

ORA-02097: parameter cannot be modified because specified value is invalid

ORA-38775: cannot disable recovery area - flashback database is enabled

取消快速恢复区，必须先禁用flashback database.

解决步骤如下：

SQL> shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup mount;

ORACLE instance started.

Total System Global Area 3206836224 bytes

Fixed Size                  2257520 bytes

Variable Size            1811942800 bytes

Database Buffers         1375731712 bytes

Redo Buffers               16904192 bytes

Database mounted.

SQL> alter database flashback off;

Database altered.

SQL> alter database open;

Database altered.

SQL> alter system set db_recovery_file_dest='';

System altered.

SQL> show parameter db_recovery_file

NAME                                 TYPE                   VALUE

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

db_recovery_file_dest                string

db_recovery_file_dest_size           big integer            6G