VTAM® issues messages that tell you whether the commands you entered were accepted or rejected. The acceptance of a command does not imply command completion. When a command is entered correctly, with valid operands, VTAM issues a message of acknowledgment. If a syntax error is made in entering a command, VTAM issues one or more error messages and rejects the command.
See z/OS Communications Server: SNA Messages for an explanation of error messages you might encounter.