ORA-01157: cannot identify/lock data file string - see DBWR trace file

ORA-01157: cannot identify/lock data file string - see DBWR trace file
Cause: The background process was either unable to find one of the data files or failed to lock it because the file was already in use. The database will prohibit access to this file but other files will be unaffected. However the first instance to open the database will need to access all online data files. Accompanying error from the operating system describes why the file could not be identified.
Action: Have operating system make file available to database. Then either open the database or do ALTER SYSTEM CHECK DATAFILES.

Reference: http://docs.oracle.com/cd/B28359_01/server.111/b28278/e900.htm#ORA-01157

ORA-01157 is raised when Database Writer (DBWR) is unable to find and lock a Datafile. This may be due to various reasons like
- Datafile is deleted or corrupt
- Datafile is renamed or moved
- Mount point is incorrect
- Issues with Read/write permission on Datafile

To solve ORA-01157 we can use one of the following steps:
- If datafile is deleted or corrupt and is not of TEMP or UNDO tablespace then we need to recoved it by using a valid backup.
- If datafile is deleted or corrupt and is not of TEMP or UNDO tablespace but that tablespace do not containt important segments, that can be dropped offline
- If datafile is renamed or moved then we need to get it in its original position
- If Mount point is incorrect, simply recreate the mount point
- if it is due to permission then we need to grant the permission at OS level

I faced ORA-01157 at my local environment, when I was restoring a cold backup. Fortunatially it was with a tablespace which was added for testing purpose and was not critical. So I simply drop the datafile using "OFFLINE DROP" clause and opened the database.

C:\>sqlplus sys/sys as sysdba
SQL*Plus: Release 11.2.0.3.0 Production on Tue Apr 30 19:07:16 2013
Copyright (c) 1982, 2011, Oracle.  All rights reserved.
Connected to an idle instance.

SQL> startup
ORACLE instance started.
Total System Global Area  778387456 bytes
Fixed Size                  1384856 bytes
Variable Size             520097384 bytes
Database Buffers          251658240 bytes
Redo Buffers                5246976 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 11 – see DBWR trace file
ORA-01110: data file 16: 'E:\oracle\app\nimish.garg\oradata\orcl\test_ts.dbf'

SQL> select NAME from v$datafile where file#=16;
NAME
--------------------------------------------------------------------------------
E:\ORACLE\APP\NIMISH.GARG\ORADATA\ORCL\TEST_TS.DBF

SQL> alter database datafile 16 OFFLINE DROP;
Database altered.

SQL> alter database open;
Database altered.

I hope this solution is helpful in solving your problem. Your comments are well appreciated.

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