Long transaction error with no-log

Hi all, I have a database with no logging under Informix-Online 7.11. This database contains a big table. When I try to update every row in this table using single UPDATE statement, it stops with error -458 Long transaction aborted caused by logical log's overfull. Why server writes UPDATE activity log for no-logging database? I don't want to increase number of logical logs because of disk space limit. More, I don't need any logging for this operation. Is there any method to work it around without dbunload/dbload - for example, switch off activity logging for this table/database? Any help would be appreciated Leonid