SSRS and Informix connection
When I use an Informix command finderr, I get the output shown:

$ finderr -23101
-23101  Unable to load locale categories.

An invalid locale name was supplied for the locale initialization.
The environment variable specifying the locale category has a wrong
value. 

Check the value of the corresponding environment variable,
CLIENT_LOCALE or DB_LOCALE. If this error was encountered when using 
the "SET COLLATION" statement, check that the value passed to the 
statement is a valid locale. If this error was encountered when using
the "SET NO COLLATION" statement, check that the session's default 
locale file is still available. Also check if INFORMIXDIR points to
a valid directory where IBM Informix products are installed.  

If a client application receives this error when it requests a database
server connection, check that the client and database locales are
compatible. They are compatible if a valid locale exists on the server
computer with the name lg_tr.codeset@mod, where lg_tr (language and
territory) and mod (locale modifier) are from the CLIENT_LOCALE and
codeset is from the database locale (from the DB_LOCALE, if it is set,
or as stored in the database).

$


That's probably clear as mud, but 'unable to load locale categories' probably means that $INFORMIXDIR, which defaults to /usr/informix on Unix-like systems (and something like C:\Informix on Windows systems IIRC) is either not set correctly or is pointing somewhere invalid.  In particular, locale categories are stored in $INFORMIXDIR/gls.

That's the easy part; the hard part is knowing what you need to set.  Have you checked the SETNET32 setting?  Have you checked the OBDC connection configuration?  I believe SSRS is a Windows-based system, and I'm by no means a Windows expert, so there's a limit to what I can do to point you in the right direction.  But having more detailed information about the error than 'unknown system error' may help you.

You could also look at the Informix manuals on the IBM Informix Information Center 12.10 web site.