Restrictions on using independent LUs

Following are some restrictions that apply to independent LUs:

An independent logical unit cannot be the destination LU (DLU) of a session, unless it is the secondary LU (SLU). An independent LU cannot function as the primary logical unit for an autologon (logappl) session. However, an independent LU can be the SLU of an autologon (logappl) session, provided that the independent LU resides on one of the following nodes:
- A peripheral (type 2.1) node that is APPN-attached to the same APPN network as the VTAM® from which the independent LU autologon session will be initiated
- A peripheral (type 2.1) node that is LEN-attached directly to the VTAM (or an owned NCP) from which the independent LU autologon session will be initiated. Autologon is not supported for independent LUs residing on peripheral (type 2.1) nodes that are LEN-attached to non-VTAM/NCP nodes (for example, when independent LUs are migrated from being NCP-attached to being DLUR-attached). This is because the independent LU autologon session is initiated by VTAM when the adjacent link station to the LEN-attached node is activated; if a LEN-attached independent LU is not directly attached to VTAM (or an owned NCP), then VTAM has no knowledge of the activation of that link station, and therefore cannot reliably initiate the autologon session.
An independent LU can initiate sessions as either a PLU or SLU.
A dependent LU can have only one active LU-LU session at a time. Thus, there is no session with the controlling application program when the LU is in session with another application program. For independent LUs, this is not the case. VTAM initiates a session between an LU and its controlling application program, even though there are already active LU-LU sessions. Each time that a session with a PLU that is not the controlling application program ends, and the independent LU does not already have a session with the controlling application program, a session is established with the controlling application program. For more information about automatic logon with independent LUs, see Automatic logons.
The name interpretation table function is not supported for independent LU sessions.
The SSCP-PU session is optional and can be requested by the type 2.1 node during the XID exchange. However, the SSCP-PU session is one of the mechanisms that the type 2.1 node uses to transport network management device information (alerts) to the SSCP for delivery to the NetView® program. An alternative mechanism used to report alerts is through a network management focal point function.