OIG 12.2.1.4.0 onwards SSO can be enabled using SAML2. Also, any other IDP that supports SAML2 can be used as well for configuring SSO login flow.
Details for the steps are provided here : https://docs.oracle.com/en/middleware/idm/identity-governance/12.2.1.4/omadm/configuring-sso-providers-oracle-identity-m…
KM Article : Doc ID 2344711.1 - OIM Support For SAML 2.0 based SSO