DC SNA Line Driver Functions as SNA Logical Unit
The DC SNA/VTAM line driver functions as an SNA logical unit. As such, the driver can maintain multiple sessions with one or more other LUs to facilitate program-to-program communication (that is, distributed processing). For example, if twenty sessions exist between a DC/UCF system and CICS, up to twenty tasks executing under DC/UCF can communicate concurrently with twenty tasks executing under CICS.
How to Define Multiple Sessions
To define multiple sessions, you include multiple physical terminals with the same VTAM node name in the DC/UCF system definition. You specify the VTAM node name in the NAME parameter of the system generation PTERM statement. The maximum number of sessions that can exist between two LUs is limited by the number of physical terminals you define. The number of sessions available at any given time is limited by the number of physical terminals that are in service.
Multiple sessions between two LUs can use different classes of service or different protocols. The protocols for a session are established by the mode table entry containing the parameters used to bind the session. You use the MODEENT parameter of the system generation PTERM statement to associate a physical terminal with a mode table entry.
Multiple Session Service Manager
To support multiple LU 6.2 sessions, the DC/UCF system must include the multiple session service manager. The service manager negotiates the number of sessions to be allowed with the remote LU.
You define the multiple session service manager with system generation PROGRAM and TASK statements:
To ensure that a session is always available to the LU 6.2 service manager, you must reserve two physical terminals:
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