IDoc or Proxy to upload 4.7 million historical data (Service Orders) to SAP CRM

Hi Experts,

Backdrop:

We are uploading 4.7 million historical data (Service Orders) to SAP CRM using SAP PI 7.0. We have this historical data from mainframe as a flat file.The total size of the flat file containing around 7 years of Service Orders will be approximately 20 GB. Each Service Order will have a Header one or more Service Items and one or more Parts Items. We are using File to IDoc scenario to post these Service Orders. We are enhancing a Standard IDoc in SAP CRM to post the data.There are 80 fields in total for each service order among them, 20 fields are standard and for the rest 60 fields we are enhancing the standard IDoc. After the historical data upload, this same interface would be used for delta upload around 5000 Service Orders Daily. We are also using 2 look ups in SAP CRM before posting the Data. The lookups will search for the existing labor code and parts. Once these

look ups are executed, the Idoc will post the data.

Please suggest if we are going for the right approach as we can use PROXY to do this. If you suggest for PROXY,

please let me know the advantage of PROXY in uploading 4.7 million

Thanks in anticipation.

Partha