The following is an extract of the online help:

About External Identities

What is an External Identity?

While logins and internal accounts are involved in the log on process, external identities are not. An external identity is an optional synchronization key for a user, group, or role. If you use batch processes to coordinate SAS identity information with your primary user registry, you need external identities (such as employee IDs) to facilitate matching. This list explains the circumstances in which a user, group, or role needs an external identity:

• For a user, group, or role that you maintain interactively in SAS Management Console, no external identity is needed.
• For a user, group, or role that you maintain using batch processes, one external identity is needed.

Where do External Identities Come From?

External identities can be added in these ways:

• For a user, group, or role that is created by an import process, an external identity is added as part of that process.
• For any user, group, or role, you can interactively add an external identity on the General tab of their definition.