Of these security systems, all of them support access through user authentication. For backward compatibility, some support a form of default identity that does not require any authentication (see Default user identity (for backward compatibility). Only ABL sessions, and database connections established from ABL sessions, support SSO operations. In addition, the ability to set the same user identity for more than one security system in a single authentication operation is supported only for ABL sessions and database connections. An ABL session can also retrieve the sealed security token from OpenEdge that was used to set the current identity for the session or any database connection established in the session.