[Zope] Permission for packing database

I would like to set up a CRON job to daily pack a Zope database. The application does some heavy text processing and consequently the database can grow half a gig per day just because of keeping all the transactions, while the data to keep is just a few megs. Because I have to type the password in clear text into the script for CRON (I intend to use wget), I'd like to create a user with a dedicated role that can do nothing, but do the packing. I could not find which permission is required for this. Can anybody tell me what the minimum privileges are for packing the database? OR can the superuser account be used for this? (With packing I mean: /Control_Panel/Database/manage_pack) Cheers Marc