The running mode of this portTopN control entry.
portTopNForeground (1) means when
portTopNTimeRemaining reaches to 0, the report
will show on the CLI at once and it won't be kept
in the portTopNTable. portTopNBackground (2) means
the report will not show on the CLI it will be
kept in the portTopNTable.
This object may not be modified if the associated
portTopNStatus object is equal to active(1).