how to active the index

I migrate the informix from 7.31 to 9.4,and I found 9.4 depant the update statistics serious. every night,I should rename a table and recreate the table and index, now the table is empty.after I insert many of row into the table,When I do a query,I found it do a sequent scan ,the index is not used.What I have to do is execute update statistics for this table. How I can use the index without execute update statistics ,except set the parameter optcomind to 0 -- Posted via http://dbforums.com