Primarily for IBM i (formerly AS/400) support of ILU-type sessions, where ILU is an 'Initiating Logical Unit'.
This common session parameter is applicable to these control statements: SYSTEM (see SYSTEM statement), PROFILE (see PROFILE statement), USER (see USER statement), TERMINAL (see TERMINAL statement), and APPL (see APPL statement).
An ILU-type session is for SNA Primary LU2 Support (SPLS) and improves the IBM i system's participation in an SNA backbone network. The initial bind from this type of session is received by IBM Session Manager as an unsolicited bind which is not accepted as the session start unless ILU=Yes is in effect.
SPLS requires one dependent logical unit (LU) definition and one ILU definition in VTAM. The ILU can be manually created, or dynamically created, depending on the release of VTAM being used.