The value of sysUpTime corresponding to the last change
to any read-create objects in this table.
The source of the change can be due to either an SNMP message
affecting this table or due to any other source of user input
such as a command line interface.
The timestamp applies to all read-create objects even for
cases where the managed device only supports read-only
access because it doesn't require user configuration of
those objects.
If there has been no change since the last time the sysUpTime
was zero then report the sysUpTime as zero.