Message IST259I received and sessions end unexpectedly

Problem statement

One or more sessions have ended unexpectedly, and a terminal, PU, line, or NCP is in a wait state.

Common symptoms

The following message is displayed:

IST259I  INOP RECEIVED FOR nodename CODE = code [text]

Probable cause

If the node is an NCP, the NCP detected an error and generated the INOP RU message.
If the node is a channel-to-channel (CTC) link or a CTC link station, VTAM® detected an error from an IO operation and generated the INOP RU message.
If the node is a local attachment device, VTAM detected an IO error and generated the INOP RU message.

User response

For an explanation of the code in IST259I, see the description of the message in z/OS Communications Server: SNA Messages.
Check the system log for system (IOS) error messages that contain status information.
If the NetView® program is installed, check NPDA for logged errors.
Run EREP against LOGREC, and check for errors related to the device.
Note: This information should identify the component causing the error. Contact the appropriate service organization for help with a specific component problem.