This read-only true/false flag indicates whether the accompanying hcxAlmDataB integer field actually contains meaningful data for this alarm row. It exists because hcxAlmDataB is a generic second data slot shared across alarm types, so the flag protects a management station from misreading an unused field. For example, an alarm that only needs one numeric value would leave this flag false, signaling the operator's tool to ignore hcxAlmDataB entirely.