FSUM2366
Input data (starting with 'string') was discarded, because the session with the shell ended.

Explanation

Input data was received from the terminal just as the session with the z/OS shell was ending. This data could not be passed to the shell. This is an informational message telling you which data was not seen by the shell.

In the message text:
'string'
The start of the input data that could not be passed to the z/OS shell. Data before this (if any) was passed to the shell.

User response

If you want to send this data to the shell, use OMVS to reestablish a session with the shell, and then reenter the data.