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Logon Address Space (LAS) functions

The LAS is required only for VTAM terminal users who log on from the terminal; the LAS is not required for EXCP or VTAM terminal sessions that are initialized by issuing an MVS START command.

Operational considerations

The following considerations apply:

  • VTAM must be available and the MainView Alternate Access VTAM application major node must be active before the LAS can be started (see Activating the VTAM application major node for more information).

  • The address space for the LAS must run as a started task and can be started by an operator or during IPL (see Starting and stopping the logon address space (LAS) for more information).

  • The startup procedure (proc) for the LAS must be placed in a JES-defined data set, such as SYS1.PROCLIB, that is referenced by started tasks.

  • Only one LAS needs to run per system; other LASs can run but must be named uniquely (see Starting and stopping the logon address space (LAS) for more information).

  • The LAS should stay active at all times; otherwise, VTAM terminal users cannot log on.

  • The LAS acknowledges the LOGON command (see Using the LOGON command for more information) or an abbreviated logon command that has been customized to your site’s USS table or logon interpret table (see Using the abbreviated logon command for more information).

When active, the LAS requests the user ID for a terminal session and issues a START command containing the user ID to initiate a TAS. After a TAS is initialized, it becomes independent of the LAS, so the LAS is not a single point of control (or failure) for a user session. Specifically, the sequence of events that occurs in association with the LAS is shown in here:

LAS operation

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