Universal containers (UC) has multiple salesforce orgs and would like to use a single identity...

The best option for UC’s architect to enable the behavior of using a single identity provider to access all of their Salesforce orgs is to ensure that users have the same Federation ID value in their user records in all of UC’s Salesforce orgs. The Federation ID is a field on the user object that stores a unique identifier for each user that is consistent across multiple systems. The Federation ID is used by Salesforce to match the user with the SAML assertion that is sent by the identity provider during the single sign-on (SSO) process. By ensuring that users have the same Federation ID value in all of their Salesforce orgs, UC can enable users to log in with the same identity provider and credentials across multiple orgs. The other options are not valid ways to enable this behavior. Ensuring that users have the same email value in their user records in all of UC’s Salesforce orgs does not guarantee that they can log in with SSO, as email is not used as a unique identifier by Salesforce. Ensuring the same username is allowed in multiple orgs by contacting Salesforce support is not possible, as username must be unique across all Salesforce orgs. Ensuring that users have the same alias value in their user records in all of UC’s Salesforce orgs does not affect the SSO process, as alias is not used as a unique identifier by Salesforce. References: [Federation ID], [SAML SSOwith Salesforce as the Service Provider], [Username], [Alias]