EQA2600E In order to SET MONITOR COLUMN OFF, you need to first SET MONITOR WRAP ON.
Explanation
SET MONITOR COLUMN OFF was issued while SET MONITOR WRAP is OFF. The command is rejected, because the Monitor window already shows the values in one, scrollable line. The Monitor window must stay in columnar format.
Programmer response
Change the setting of MONITOR WRAP to ON, and then issue SET MONITOR COLUMN
OFF
.