出现问题：
SQL> startup;
ORACLE instance started.

Total System Global Area 2371719168 bytes
Fixed Size 2215624 bytes
Variable Size 1342177592 bytes
Database Buffers 1023410176 bytes
Redo Buffers 3915776 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 6 - see DBWR trace file
ORA-01110: data file 6: '/opt/oracle/oradata/orcl/srcmsg.dbf'

解决办法：
1.关库
SQL> shutdown immediate;

2. alter database open
   ORA-01157: cannot identify/lock data file 10 - see DBWR trace file
   ORA-01110: data file 12: '/oradata/orcldata/sacproduce02.dbf'
   报错信息为不能进行读写操作，挂载的硬盘不能进行读写操作了。要打开数据库，只能将该文件进行离线操作了。
3. SQL> archive log list; //查一下数据库的归档模式，
   Database log mode No Archive Mode //非归档模式
   Automatic archival Disabled
   Archive destination USE_DB_RECOVERY_FILE_DEST
   Oldest online log sequence 4
   Current log sequence 6
   若归档模式下，则：
   alter database datafile '/oradata/orcldata/sacproduce02.dbf' offline
   非归档模式下（现在情况）
   alter database datafile '/oradata/orcldata/sacproduce02.dbf'offline drop
   SQL> alter database datafile '/opt/oracle/oradata/orcl/srcmsg.dbf' offline drop;

Database altered.

SQL> alter database datafile '/opt/oracle/oradata/orcl/srcmsg.dbf' offline;
Database altered.
最后打开数据库就可以了