SAP 8.8 - Database Upgrade

Hi,

I'm trying to update a database from a client (version 2007a PL09) for SAP 8.8 version but without success. When the update finishes we get the error "Inventory Valuation Log". I made the IVC and also the message obtained is "Null value is eliminated by an aggregate or other set operation. System does not use perpetual inventory". Why the reason?

Thanks.

Regards.

Sandra Pereira