Abendu2222 reason code 1 is issued whenever a user server was terminated without first stopping one or more REXX environments that are still running at the time of termination. In that case, task control blocks (TCBs) that are left hanging will not terminate on their own, causing the address space to hang during termination. In that case, the address space will need to be canceled.
This usually happens when an ISPF application encounters a problem and does not send a good explanation to the client or is now in an undefined state. It can also happen when a command was issued in the user server that is listed in the installation’s IKJTSOxx parmlib member under PLATCMD or PLATPGM. z/Server does not tolerate commands executed under the platform TCB as it requires MVS services for task termination (clean-up).
To prevent subsequent abnormal end problems, z/Server terminates all tasks that should not be running anymore using reason code 1.