Way to keep Serial Number in Sink
I am working with Serial number profile with process given below
1. There is one system which is non SAP where we are creating stock with Serial Numbers.
2. Through I-Doc all the data is coming to SAP.
3. we are creating material document with reference with data coming through I-Doc. (same serial no is used which is created with non SAP System).
4. But the problem i am facing to keep both system in Sink with serial numbers. I found one problem that user made GR manually in SAP with serial no and while I-Doc run system give me error that serial no profile is already created.
Can anybody tell me various ways or steps to keep both systems in Sink.
Thanks in Advance.