In NetApp ONTAP SnapMirror asynchronous replication architectures, replication health is fundamentally evaluated by tracking the relationship's lag time. Lag time represents the difference between the current time and the timestamp of the latest Snapshot copy that has been successfully transferred and committed to the destination volume.

A healthy, scheduled SnapMirror relationship operates properly when its lag time remains strictly less than the update frequency defined in its replication schedule. For example, if an asynchronous SnapMirror schedule dictates transfers every 60 minutes, a lag time under 60 minutes confirms that replication transfers are completing successfully on schedule and the secondary site satisfies its Recovery Point Objective (RPO). If the lag time exceeds the schedule interval, it indicates replication failure, network congestion, or aborted transfers. An "idle" relationship status merely denotes that no active transfer is occurring at that moment, which could occur even if the relationship is failing. An unidentified peer cluster indicates broken peering, and mismatched Snapshot timestamps do not directly validate replication compliance.