Connecting to IMS

Before a user can use a terminal, the master terminal operator (MTO) must initialize the communication network using one or more of the following commands: /START DC, /START NODE, and (possibly) /OPNDST for VTAM® terminals.

Terminal startup for nonswitched lines

For startup to be successful, the remote terminal must be turned on. IMS notifies the remote terminal of a successful /START or UPDATE command with the DFS059 terminal started message. Communication with IMS can only begin after the startup message is received.

Exception:   A remote terminal can communicate with the following terminals before receiving message DFS059: the master terminal, physical terminals on the master terminal line, and the system console.

VTAM terminals (nodes)

SLU type P, FINANCE (3600), and ISC terminal systems do not receive IMS-generated connect messages. Instead, they communicate with a user-written program that resides in the terminal system's storage. Type-1 SLUs in unattended mode also do not receive connect messages (because there is no operator to receive the message).

VTAM terminals receive message DFS3649, DFS3650, or both. The DFS3649 message requests signon information, and the DFS3650 message indicates successful signon (or connection) and session status. Message DFS3649 also appears in the following situations: when failures occur during the signon process, when the operator signs off, or (for ETO only) automatic session timeout due to inactivity.

Releasing VTAM terminals hung in I/O

Use the /TRACE command to specify what action, if any, IMS should take when it determines that a VTAM response has been outstanding for a longer time than you specify. This facility applies only to VTAM devices that have VTCBs or MSC links.

IMS can handle outstanding responses in one of the following ways:

  • No action.
  • Issue a message that I/O has been outstanding for a longer time than you have specified; that is, the device has timed out.

    In this case, the operator must determine what action, if any, to take. For example, the MTO or an AOI program could issue an /IDLE command followed by an /ACTIVATE command and an /OPNDST command.

  • Issue a message that I/O is outstanding followed by a VTAM VARY NET,INACT command to deactivate the terminal, and a VTAM VARY NET,ACT command to reactivate it. If the device is operable and defined to IMS as non-shared, and IMS is not shutting down, IMS issues a /OPNDST command to establish a session with the node.

Use the /DISPLAY command to display all the nodes that have I/O which has been outstanding for a longer time than was specified during installation. The /DISPLAY TRACE command displays the status of all nodes that have I/O outstanding for a longer time than you specified using the /TRACE SET TIMEOUT command.

Fulfilling security requirements

Depending on the security options specified for the system, the end user might need to use the /SIGN command to provide a user ID for verification by IMS or RACF® and supply an IMS or RACF password. Users with ETO terminals must use the /SIGN command. You need to document the security procedures the end user must follow.