RP:
I'm not understanding your question. By definition, informix includes a rowid which is valid for the life of a row:
select rowid, * from some_table
includes the integer rowid.
If you are using table fragmentation the rowid must be built separately. Sorry, I have no experience in this area.
Informix and others suggest not using the rowid because of portability issues, changes in the future, etc.
Regards,
Ed