SQL Server 2019 Mirroring delays

Hi eric_stephan-sk​,

I would be careful about assuming the one-hour delay is something you can solve by changing the backoff interval.

Microsoft describes the backoff logic as part of how Fabric Mirroring reduces unnecessary load on external source systems when activity is low. I could not find a documented setting that allows you to disable it or force every table to be polled on the same fixed cadence.

For SQL Server mirroring, Microsoft still describes incremental replication as near real time, so repeated hour-long delays on tables that are actively changing are worth investigating rather than treating as expected behaviour.

I would first separate where the latency is occurring. In the replication monitor, compare each table's Last completed timestamp with the time the source change actually occurred. If you enable workspace monitoring, the mirrored database logs expose ReplicatorBatchLatency at table level, which is useful for identifying whether the lag is occurring during replication itself.

Microsoft's mirroring troubleshooting guidance also recommends checking whether the data has already reached OneLake. If it is present in OneLake but not visible through the SQL analytics endpoint yet, the delay may be metadata synchronization rather than mirroring.

I would also compare a quiet table and a busy table using the same source and gateway. If both show high replication latency, I would investigate the gateway/source path. If only specific tables show the delay while others continue replicating normally, that gives you a stronger case to take to Microsoft support with the table-level monitoring logs.

For downstream fact/dimension processing, I would not assume that mirrored tables arrive transactionally in sync with one another. I would add a freshness gate or watermark check before starting the dependent workload, especially where a fact table relies on a dimension change being present first.

So my approach would be to treat backoff as service-managed, measure the actual latency by table, and escalate persistent hour-long lag on actively changing tables rather than trying to force a uniform polling interval.

AI-assisted drafting: AI was used to help structure and phrase this response. I reviewed and validated the technical content before posting.