Oracle ORA-01157: unable to identify/lock data files

Create undo tablespace MOZI datafile 'e: \ Oracle \ product \ 10.2.0 \ oradata \ orcl \ MOZI. dbf' size 2048 M extent management local;
Alter system set undo_tablespace = MOZI;
The ORCL database in WINDOW prompts: the database is not open: it can only be queried in fixed tables/views.
An error occurred while loading the database:
RA-01157: unable to identify/lock data file 7-see DBWR trace file
ORA-01110: data file 7: 'd: \ TCM52.DBF'
SQL> startup
The ORACLE routine has been started.

Total System Global Area 293601280 bytes
Fixed Size 1290208 bytes
Variable Size 209715232 bytes
Database Buffers 75497472 bytes
Redo Buffers 7098368 bytes
The database has been loaded.
ORA-01157: unable to identify/lock data file 7-see DBWR trace file
ORA-01110: data file 7: 'd: \ TCM52.DB <span class = "hilite"> F </span>'
Cause: When I stop the data service, I will delete the data file D: \ TCM52.DBF.
Solution:
SQL> startup
The ORACLE routine has been started.

Total System Global Area 293601280 bytes
Fixed Size 1290208 bytes
Variable Size 213909536 bytes
Database Buffers 71303168 bytes
Redo Buffers 7098368 bytes
The database has been loaded.
ORA-01157: unable to identify/lock data file 7-see DBWR trace file
ORA-01110: data file 7: 'd: \ TCM52.DBF'

SQL> alter database datafile 'd: \ TCM52.dbf 'offline drop;
The database has been changed.

SQL> alter database open;
The database has been changed.

SQL> drop tablespace TCM52 including contents;
The tablespace has been deleted.

SQL> create undo tablespace TCM52 datafile 'e: \ oracle \ product \ 10.2.0 \ oradata \ TCM52.db <span class = "hilite"> f </span> 'size 2048 M extent management local;
The tablespace has been created.

SQL> alter system set undo_tablespace = TCM52;
The system has been changed.
A similar problem occurs in LINUX,