IFILE

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As many know, ifile can be used as an initialization parameter in init.ora to
include other parameter file. As with any parameter that can be specified
multiple times to include more items (such as event, utl_file_dir,
rollback_segments, etc.), multiple ifile lines must be contiguous, not
separated by even a comment line.

#This works:
ifile=file1
ifile=file2

#This doesn't work.
ifile=file1
#some comment
ifile=file2

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Those parameters that require contiguous lines cannot be separated across
the current init file and a file that gets included in through ifile. For
instance, a line "event='10704 trace name context forever, level 10'" is in
common.ora and your init.ora has:

ifile=common.ora
event='10046 trace name context forever, level 12'

Even if the event set in common.ora is the last line in it, it will be
ignored. You can check by `show parameter event' after the database is up.

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The above restrictions do not apply if you create an spfile from the
pfile (init.ora) with ifile line(s). An spfile is created by merging all
non-comment lines in the pfile and the lines referenced in ifile(s), sort
them alphabetically, prepend *. if not yet. When the database starts up,
this one single spfile is read.

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Although undocumented, ifile directive works fine in listener.ora, sqlnet.ora,
and tnsnames.ora. It's particularly useful in tnsnames.ora, because it allows
you to deploy a common set of TNS aliases to your clients while having the
flexibility of maintaining a host specific set of TNS entries. Suppose your
organization has a common O: drive mapped to a network share where you have
commontns.ora, you can set ifile=o:\commontns.ora above the client host
specific entries. As usual, the same-name entry added last overrides the
previous one.

SEE ALSO

* http://www.freelists.org/post/oracle-l/IFILE-directive-for-tnsnamesora,14

* "Bug 7295657: 10G: LEVEL OF NESTING OF TNSNAMES VIA IFILE":
----- begin quote -----
    Conclusion:
    Hence only one level of Indirection works, let me know if you want to 
purse the issue with development.
    
    References for IFILE configuration in tnsnames.ora
    Note 91990.1:  Using an iFILE to Configure SQL*Net/Net8/Net Services  
Connectivity
----- end quote -----

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