Diagnosis
You have assigned an InfoOject (BW system) to the field (data element)from the DataSource (source system). However, this field from theDataSource was not replicated from the source system.

Procedure

Checks and corrections in the BW system (Administrator Workbench:Transfer rules for InfoSource)
Check the transfer rules and the transfer structure in the BW system.
Was the DataSource replicated correctly into the BW system?
If an InfoObject is assigned incorrectly to the DataSource (sourcesystem) field, delete the field from the transfer rules and thetransfer structure.
Reactivate the transfer rules for the source system, after making thecorrections in the BW system.

Checks and corrections in the source system (DataSource maintenance:Transaction RSA2)
If an InfoOject is assigned correctly to the BW system field, check theDataSource fields in the source system and, if applicable, adjust them.
Has the field been flagged in the DataSource maintenance as selection'A' (Hide OLTP and BW) by mistake?
After making the corrections in the source system, replicate theDataSource into the BW system again.