Problem Description:
====================

An ORA-01157 is issued whenever Oracle attempts to access a file but cannot
find it:

ORA-01157: "cannot identify data file %s - file not found"
Cause: The background process was not able to find one of the data files.
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 file was not found.
Action: Have operating system make file available to database. Then either
open the database or do ALTER SYSTEM CHECK DATAFILES.

ORA-01157 errors are usually followed by ORA-01110 and possibly an Oracle
operating system layer error such as ORA-07360. A DBWR trace file is generated
in the background_dump_dest directory.


Problem Explanation:
====================

Oracle tries to open all datafiles when you issue a STARTUP or ALTER DATABASE
OPEN. If a datafile cannot be found at this point, an ORA-01157 results.

There are two main possible causes for an ORA-01157 on startup:

1. The datafile does exist, but Oracle cannot find it.

1.A) It may have been renamed at the operating system level, moved to a
different directory, disk drive, etc. In this case, simply restoring the
datafile to its original name and location will solve the problem.

1.B) You intentionally moved the datafile to a different location, but forgot
to rename it at Oracle level. For example, you may have decided to move
the index tablespace datafiles to another disk to improve performance, but
forgot to rename them inside Oracle. In this case, you must rename the
datafile(s) from within Oracle.

2. The datafile has been physically removed or damaged to an extent that
Oracle cannot recognize it anymore.

In this case, that datafile is lost and the solution depends on the type of
datafile involved, i.e., on the tablespace to which the datafile belongs.


Solution Description:
=====================

There are two types of solutions for an ORA-01157:


I. THE DATAFILE IS LOST OR TOO DAMAGED
--------------------------------------

In this case, the solution depends on the tablespace to which the datafile
belongs. Look for a Solution Reference matching the type of datafile lost.


II. THE DATAFILE HAS SIMPLY BEEN MOVED OR RENAMED
-------------------------------------------------

If you originally wanted to change the name/location of the file, look for the
Solution Reference on how to rename datafiles inside Oracle. If the file has
been moved or renamed by mistake, simply restore it to its original
name/location and startup the database.