Hi,
such functionality has never been implemented ( at my knowlege), in an RDBMS ...
As you say, it would take a long time to run and also incomodate other users due to performance loss.
In any case, you can try to write some perl script, using DBI::Informix, read the systables and sycolumns tables to get the column names, do a huge foreach and all those names, then PREPARE and EXECUTE each query with the your where clause.
But again, a RDBMS is not designed and built for such a query. RDBMS is for organized data, not for unorganized data. The performance loss will severely impact all the other users connected.
unless you Informix engine is SE, where you can egrep the .dat files ...
Google desktop could also be a good solution if using .dat files ...
No other idea from here :-(
Eric