free up disk space

Dear Informixers, I have a problem: How to free up extents that have been allocated to tables without restarting application that has cursor defined on the tables? We are using Online 5.0 on HP-UX. The datababase is to record some kind of daily activity. The data is accumulated but only some recent data should be kept. Old data is deleted everyday. I have found even the data is deleted, the disk space is not freed for others to use. I realized that reload the table or even create a cluster index will help the free space to actually be freed. But applications that uses the table in some cursor will have to be restarted, that is not possible. Could somebody help me to solve this problem: How to free disk space with out affect the cursor that has been defined for the tables? Thanks in advance! Wendy