create procedure "informix".test()
-- ...код...
foreach cur for select tmp_discount_rate.amount, tmp_discount_rate.param, tmp_discount_rate.credMonths
			into amount, param, credMonths
			from tmp_discount_rate

			let persResult =  0 ;
			let persBuf = param /  100  /  360  *  30 ;
			let iPayPerMonth = amount;
			let iPersPerMonth = amount * persBuf;
			let persResult = persResult + iPersPerMonth;

			for i =  2  to credMonths step  1 
				let iPayPerMonth = iPayPerMonth / credMonths;
				let iPersPerMonth = (amount - iPayPerMonth) * persBuf;
				let persResult = persResult + iPersPerMonth;
			end for;
			
			update tmp_discount_rate set
				tmp_discount_rate.persPerMonth = persResult
			where current of cur;
		end foreach

create temp table tmp_discount_rate(.....) with no log

BEGIN WORK;
foreach cur for select tmp_discount_rate.amount, tmp_discount_rate.param, tmp_discount_rate.credMonths
			into amount, param, credMonths
			from tmp_discount_rate
-- bla-bla-bla
end foreach
COMMIT WORK;