When customers transition from on-premise SAP system to Cloud they are hesitant to either continue their integrations from on-premise or move to cloud. One of the biggest reason for this is that they have already invested a lot in their integrations Landscape from on-premise systems via SAP middleware i.e. SAP PI.
Few customers decide to go with SAP PI as their first choice for all integrations from ECP. Others decide to go with SAP Cloud Platform Integration (CPI) and there are few who go with both at the same time.
Scenario 1 - Customer doesn't want to use SAP CPI
All outbound integrations from ECP should send the data to vendor as well as write the file on their internal network drive (inside the customer landscape/ DMZ) which is in customer's landscape.
Data from ECP can be sent via idoc to SAP PI which further sends the data to vendor and archives the file via SFTP. Custom message types can be build in ECP as per interface mapping.
In the above figure, ECP sends idoc to SAP PI via an ABAP Connection i.e. Connection type 3 (refer below screenshot).
The target host in the RFC connection points to SAP PI as shown below.
Scenario 2 - Customer wants to use SAP CPI along with SAP PI
Customer wants to use SAP CPI to interact with all vendor systems and also wants to archive data in its network drive which is only accessible via PI. It is not advisable to use 2 middleware but it may be required as every customer has a different requirement for different reasons and policies behind it.
In this case both SAP PI and SAP CPI will be utilized in the integrations as shown below.
2.1) via SOAP from ECP
SAP CPI can send the data to SAP PI via SAP Cloud Connector. SAP PI can then archive the data in internal network drive.
2.2) via Flat file from ECP
An RFC can be created in ECP system to point to SuccessFactors SFTP. Every customer gets a personal SF SFTP with the license.
ECP can write the data in file format on SF SFTP from where SAP CPI can pick the file and pass on to vendor.
SAP CPI also sends this data to SAP PI via SAP Cloud Conector for archival.
In the above figure, ECP writes data to SF SFTP via RFC of Connection type G i.e. HTTP connection to External server. The target host points to the SFTP server. Example shown below.
Note - ECP can write the file on application server ( accessed via transaction code AL11). An ABAP program can be developed ECP to read the data from application server and write on SF SFTP via this Type G RFC. This program can be scheduled accordingly.
If the file needs to be archived on the Customer's on-premise SFTP server then SAP CPI can also do that. There's a solution which SAP has given in Nov 2018 release. Refer this blog for more information.
Here's the link of my blog for Inbound Integration approach to ECP.