CASTS1020I ES is configured to discard unsolicited CICS TN3270 input
Enterprise Server CICS terminal control is configured to discard all unsolicited TN3270 messages, i.e. it will discard TN3270 messages that arrive while a transaction is active for the target terminal unless the transaction has issued an explicit CICS RECEIVE after the first CICS terminal control command. For messages that arrive while the terminal is idle, ES will attempt to start a transaction for the message.
