Recovering from a network failure when the remote terminal stops responding

If IMS stops responding to a remote terminal, you might be able to recover the session if the IMS master terminal is still active. The MTO receives a message that indicates why the terminals are not operational if they have not been stopped by the /CLSDST, /STOP, or /PSTOP commands. Correct the error and issue a /START or /RSTART command to restore operation for the terminals.

You can use the various forms of the /DISPLAY command to list the status for communication lines, terminals, nodes, and ETO dynamic users.

  • Use the /DISPLAY LINE command for communication lines
  • Use the /DISPLAY LINE PTERM command for terminals
  • Use the /DISPLAY NODE command for nodes
  • Use the /DISPLAY USER command for ETO dynamic users

For a VTAM® terminal session, you might only need to use the /OPNDST NODE command to restart it.

If you have a hung node, you can free it with a /CLSDST FORCE command, if the following conditions exist:

  • A VTAM display indicates that no session exists.
  • The output from a /DISPLAY NODE command indicates that a CID exists, the node is connected, and the node is not idle.

    If a session does exist, terminate it with the VTAM command VARY INACT,FORCE, but use caution, because this command terminates all parallel sessions.

If a static node or ETO dynamic user is hung in Fast Path input response mode, as indicated by a RESP-INP-FP status in the output of the /DISPLAY NODE or /DISPLAY USER commands, you can reset the node or user with the appropriate /STOP and /START command sequence. For static nodes, issue /STOP NODE and /START NODE. For ETO dynamic users, issue/STOP USER and /START USER.

If a static node or ETO dynamic user is hung in full-function input response mode, as indicated by a RESP-INP status in the output of the /DISPLAY NODE or /DISPLAY USER commands, you can reset the node or user with the /DEQUEUE command to discard response-mode output so that the /RSTART command can reset terminal response mode.

If all terminals are operational and appear to function, then it is likely that an application program has terminated abnormally, or is in a loop, or has a resource conflict that prevents its scheduling. To find the cause of the problem, use one of the following commands: /DISPLAY ACTIVE, /DISPLAY PROGRAM, /DISPLAY TRAN, or QUERY TRAN.

If you use /DISPLAY ACTIVE and continually see a program listed as active in a MPP or BMP region, that program is probably in a loop. For a program that is continually active, check that its PROCLIM value (specified in the PSB) is correct. Use the /STOP REGION ABDUMP command to terminate the region, or use the /STOP command to stop programs and transactions. You should be careful when using the /STOP REGION CANCEL command because in certain instances it can cause an abend of the IMS control region.