A desired threshold for the number of Unavailable Seconds (UAS)
within any given 1-day performance data collection interval.
If the number of UASs in a particular 1-day collection interval
reaches or exceeds this value, a gBondPmTca1DayUASCrossing
notification MAY be generated if enabled by
gBondPortConfPmTcaEnable.
At most one notification can be sent per interval.
Setting this attribute to zero (default) effectively disables
gBondPmTca1DayUASCrossing notification.
This object maps to the TR-159 attribute
aGroupPerfThreshold1DayUAS.