If you have more than one Management Point on your Active Directory Site, or you had old SCCM or SMS site system and you deploy a new site site system with a new Management Point without removing old Management Point from System Container in Active Directory.
You may found the following warning in Site Status -> SMS Management Point
MP has discarded a report when processing Ddr
Possible Cause: Corruption or invalid user definition.
Solution: Check the logs to identify the cause. If the problem is persistent raise the issue with Microsoft Support.
The error or warning "MP has discarded a report when processing Ddr" happens because the "old" clients are trying to send inventory/discovery data to the new MP. This is because System container in Active Directory Users and Computers contain both the old Management Point attribute and the new Management Point attribute.
So if you have old Site System server and you deploy a new SCCM server with new site system and a new Management Point, this issue will occur.
So the problem should be the "old" clients are trying to send inventory/discovery data to the new MP. What we need is for the old MP to be removed, and start afresh with the new MP.
To solve this issue, please try the following steps:
1- Log on to Domain Controller with admin account.
2- Open Active Directory Users and Computers.
3- Click view then advanced future.
4- Highlight "system management" container underneath domain.com-system.
5- Check if there is item with name "SMS-MP-site Code-machinename", just delete the record with discarded MP machine name.
6- Restart the site server and Management Point.
Ideally, before going to install or deploy a new site system, it's recommended to delete old records before starting, and that way avoid the problem above.
For more information, read up on the System Center Configuration Manager : http://technet.microsoft.com/en-us/library/bb735860.aspx
Before you begin, you would be advised to read up on the trouble shooting guides : http://technet.microsoft.com/en-us/library/bb632812.aspx
DDR errors can also be due to unresolvable IP addresses as shown in the "Troubleshooting Discovery" topic in the above link.
Hope you find this Article of help.