The ON_ERROR procedure determines the action taken when an error is detected inside an IDL user procedure or function by setting state information applying to the current routine and all nested routines. If an override exists within the nested routine, it takes precedence over the ON_ERROR call.
ON_ERROR, N
An integer that specifies the action to take. Valid values for N are:
None.
Introduced: Original
CATCH, MESSAGE, ON_IOERROR, and Controlling Errors.