Hello Rebekah,
I am sure you know these steps. But repeating it here.
1. Create Source System
2. Create Data Source
3. Create Infopackge based on the Data Source
4. You create Infocube or DSO.
5. Then you create data transformation for mapping fields between Data source and Data Target (DSO or Infocube)
6. Then you create Data Transfer Process(DTP) where you define Target and Source for DTP, Extraction Mode(Full/Delta) etc.
In DTP you have option of activating Error Handling, you also need to create Error DTP in the same screen. This will help you know whether you have any erroneous records which is causing data transfer to fail.
Please check.
Thank you
Satish Waghmare