This read-only counter measures the number of high-priority ATM cells discarded when the system's internal buffers overflow, indicating the board has run out of memory. Network engineers watch this closely because high-priority losses (video, voice) mean the system is severely congested—even though these cells should not be dropped, they are being lost, causing service degradation. An increasing OVFL counter during business hours signals that the matrix board's buffer capacity is inadequate for peak traffic, requiring either a hardware upgrade or traffic engineering changes.