Instance administrators can configure available authentication schemes for an Oracle APEX instance.
The authentication scheme designated as Current determines how Oracle APEX identifies and verifies instance administrators, workspace administrators, and developers. Depending upon the selected authentication scheme type, you can configure various settings to fine-tune authentication behavior.
Even for external authentication schemes (such as HTTP Header Variable), make sure that users exist as developers or administrators in your workspace. Otherwise, APEX will not be able to verify in which workspace a user is allowed to work.
You can also change the authentication scheme using the
APEX_BUILDER_AUTHENTICATION parameter in
APEX_INSTANCE_ADMIN package. See APEX_INSTANCE_ADMIN, Available Parameter Values in Oracle APEX API