You want to upsert an attachment through oData API into specific user's background, however you're getting an error: "Property attachment is not upsertable"
- In order for you to know if its possible to do an upsert for a specific field, you can go to OData API Data Dictionary.
- We have verified that attachment is not upsertable for Background Entity as it is set to 'False'.
SAP SuccessFactors HCM Suite OData API: Developer Guide
SAP SuccessFactors Employee Central OData API: Reference Guide
OData API, Attachment, Background Entity , KBA , LOD-SF-INT-API , SF API & Adhoc API Framework , LOD-SF-INT , SF Integrations - EC Payroll, Boomi/ HCI, API , Problem