Session initiation (starting workstations)

A session is the logical connection of a workstation to a VTAM® application program, such as IMS or the system utilities. A session must be established before data can be transmitted between a workstation and IMS. Message resynchronization is performed during session initiation, unless IMS is cold started.

Session initiation can be requested in one of the following ways:
  • The workstation requests session initiation by sending the INITIATE-SELF command. VTAM verifies the command and passes the request to IMS. If the terminal is requesting a session with an IMS XRF complex, the IMS USERVAR name or the MNPS ACB should be used for the application name.
  • The z/OS® VTAM network operator requests session initiation on behalf of the workstation by using the VTAM VARY command with the LOGON option. VTAM processes the request and passes it to IMS.
  • VTAM passes a logon request to IMS for each workstation that is defined to VTAM as belonging to IMS.
  • The IMS master terminal operator requests session initiation for a workstation by entering the IMS /OPNDST command.

Regardless of how session initiation is requested, identical processing occurs when IMS receives the request.