The relativeLatency is the latency between now and timestamp of the last event written into the local THL. This information gives an indication of how fresh the incoming THL information is. On a master, it indicates whether the master is keeping up with transactions generated on the master database. On a slave, it indicates how up to date the THL read from the master is.
A large value can either indicate that the database is not busy, that a large transaction is currently being read from the source database, or from the master replicator, or that the replicator has stalled for some reason.
relativeLatency on the
slave may indicate that the replicator may have stalled and
stopped applying changes to the dataserver.