Login_user   When Login_user is specified, the database server always uses the logged in user's extern login credentials when making remote data access connections, regardless of what the current effective user is.

Effective_user   When Effective_user is specified, the database server respects the setting of the current effective user. Remote data access connections are established based on the extern login credentials of the current effective user rather than always using the extern login credentials of the logged in user. Specifying Effective_user may result in multiple (one per effective user) remote connections for the same local connection.