This read-only value reports the currently available outgoing virtual bandwidth within the QoS Class 3 reservation, the unused portion of lportAtmDataRateQoS3's total reservation for that traffic tier. An admin uses this when admitting new class-3 connections, like business-critical data circuits, to this port, verifying sufficient reserved capacity remains before adding load to that class. For example, a low lportOutVAvailbwQoS3 reading would tell the admin the class-3 reservation on this port is nearly fully committed, making it a poor candidate for another business-data circuit without first increasing lportAtmDataRateQoS3.