This is the cumulative inbound frames discarded counter: counts FC frames this port accepted off the wire but then dropped internally, typically because of a full receive buffer or a frame header the ASIC could not parse. On one specific historical error-statistics snapshot for an FC port, this is the lifetime tally, so climbing discards on an otherwise up port usually mean the port is oversubscribed for its buffer credits, which shows up to hosts as SCSI retries rather than link errors. For example, a target-facing port pinned near its buffer-to-buffer credit limit during a backup window discards 120 frames in an hour, then returns to zero once the backup finishes.