Hi Sharath,
Users authenticating via Social Sign-On for the first time are new or unknown to SiteMinder and are not included in the SiteMinder user store. SiteMinder can handle this situation in two ways:
1. Initiate a dynamic user provisioning flow to handle self-registration.
2. Reject such requests as “unknown” users.
Dynamic user provisioning is implemented by redirecting users to an external provisioning URL where an external provisioning system handles the self-registration flow.
Considerations are required to enable the external provisioning system to gracefully handle the entire flow, including retrieval of user attributes gathered from the Social provider and handling a redirect back from the provisioning system back to SiteMinder once the self-registration flow is completed.
Please refer below links for more details.
SAP Portal Services
User Provisioning at the Relying Party
Thanks,
Sharan