ORA-1142 signalled during: ALTER DATABASE END BACKUP...

WARNING: datafile #849 was not in online backup mode
WARNING: datafile #850 was not in online backup mode
WARNING: datafile #851 was not in online backup mode
WARNING: datafile #852 was not in online backup mode
WARNING: datafile #853 was not in online backup mode
WARNING: datafile #854 was not in online backup mode
WARNING: datafile #855 was not in online backup mode
WARNING: datafile #856 was not in online backup mode
WARNING: datafile #857 was not in online backup mode
ORA-1142 signalled during: ALTER DATABASE END BACKUP...
解决办法：
如果对数据库设置为结束热备份时日志中才会报以上错误日志信息，因为没有把数据库设置为开始热备份的状态。

SQL> alter database end backup;
alter database end backup
*
第 1 行出现错误:
ORA-1142 signalled during: ALTER DATABASE END BACKUP...

SQL> alter database begin backup;

数据库已更改。

SQL> alter database end backup;

数据库已更改。

则数据库日志报以下信息，不再出现警告信息

alter database begin backup
Completed: alter database begin backup
alter database end backup
Completed: alter database end backup