Upgrade Procedure/R/3 Support Packages 
During an upgrade or an import of R/3 Support Packages, existing objects of the SAP standard are overwritten by new objects delivered. In order to help customers keep those objects that have been modified in a previous release, SAP now offers upgrade adjustment for all objects being upgraded in the form of transactions SPAU and SPDD. These transactions allow customers to enter their modifications into the corresponding new objects being delivered at upgrade. The Modification Assistant supports this process of adopting customer modifications.
In the past, all objects modified by a customer and delivered again by SAP, an IBU or an SAP partner, had to be manually re-modified during an upgrade. Now, modifications are either automatically adopted or the system provides you with an assistant for adjusting your modifications to the newly upgraded configuration.
In general, objects altered using the Modification Assistant can now be automatically accepted into the upgraded system if the modifications undertaken in the original version do not directly overlap those made in the customer version. If collisions occur between the two versions at upgrade (naming collisions, or if SAP has deleted an object modified by a customer), the system offers semi-automatic adjustment support. In some cases, however, you may still have to manually adjust objects using ABAP Workbench tools.
Objects modified according to the old system used prior to the advent of the Modification Assistant must be manually maintained after an upgrade has been run.
Use transactions SPDD and SPAU during an upgrade to select these objects and modify them manually.
For more information, refer to:

ABAP Dictionary objects modified using the Modification Assistant can be adjusted in transaction SPDD (see
Modifications in the ABAP Dictionary).In addition, transaction SPAU allows you to adjust ABAP Dictionary objects where no data loss can occur, specifically:
Additional information about the modification adjustment procedure using transaction SPAU can be found in Adjusting R/3 Repository Objects.
Additional information about upgrade procedure can be found in:
Upgrading From Release 4.5A or Less
Modifications Made by Several Different People
Upgrading the Development System
Upgrading the Production System Handling Change Requests During Adjustment Choosing a Change Request for Modifications Local and Transportable Change Requests Releasing Tasks at the End of Modification Adjustment Choosing a Change Request to Transfer Modification Adjustments to Other SAP Systems Notes (Troubleshooting)