Immediate termination

The IMS master terminal operator uses the /CHECKPOINT command with the FREEZE, PURGE, or DUMPQ parameter, but without the QUIESCE parameter, to invoke immediate termination of the network. IMS issues the VTAM CLSDST macro instruction. CLSDST causes VTAM to issue the UNBIND command to all workstations. This command releases the workstation from session with IMS. The controller prohibits any further data transmission from the workstation.

To terminate workstations or portions of a network selectively, the IMS master terminal operator can use the IMS /CLSDST or /STOP command. /CLSDST and /STOP commands cause IMS to issue the VTAM CLSDST macro instruction for the specified workstations. The /STOP command also prevents further sessions from being established until a /START command is issued for the workstation.

The z/OS® VTAM network operator uses the VARY command to terminate a workstation immediately. z/OS VTAM network operator intervention using the VARY command might be required to terminate sessions in which a workstation error prevents an I/O operation from completing.

The workstation uses VTAM session control commands to terminate a session with IMS. Under normal processing circumstances, when the workstation decides to terminate its session with IMS, that workstation should send the VTAM request-shutdown command. IMS completes any input or output currently in progress for that workstation and then issues the VTAM CLSDST macro instruction.

If the workstation detects an error condition from which it cannot recover and then wants to terminate the session, it can send the VTAM terminate-session command. VTAM releases the workstation from the session and notifies IMS accordingly.