Link security further restricts the resources a user can access, depending on the remote system from which they are accessed. The practical effect of link security is to prevent a remote user from attaching a transaction or accessing a resource for which the link userid has no authority.
When link security is in use, each session is given an authority defined by a link userid. For LU6.2, all sessions in a connection can have the same link userid, or different groups of sessions within the connection can have different link userids. You can also specify that some groups of sessions should use link security, and that others should not.
If a failure occurs in establishing link security, the link is given the security of the local region's default user. This would happen, for example, if the preset session userid had been revoked.