Hi,
Some initial Questions from my side.
1. Which SRM version are you on?
2. What is your erp version defined in System Landscape system type?
Note : If its above erp_4.0 then Contract goes via webservices and SA via idoc , otherwise everything goes via idocs.
3. What are you transferring Contracts or Scheduling Agreements?
Note : If Central Contract - It gets transferred via webservices ( PI/Non PI) and if its SA then it gets transferred via IDOCS ( distribution model needs to be created in ECC) all this for SRM 7.0 and ECC EHP4 onwards.
Regards,
Naveen