The UEVENT Statement uses ON, OFF or STOP to enable, turn off or suspend user event trapping.
Syntax
UEVENT {ON STOP OFF} 
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    UEVENT ON enables user defined event-trapping as defined by the ON UEVENT statement. 
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    UEVENT OFF disables the event-trapping routine. All events are ignored and are not remembered. 
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    UEVENT STOP suspends the event-trapping routine. An event is remembered, and the event-trapping routine will be performed as soon as a UEVENT ON statement re-enables the trapping.