Data Monitoring / SQL Server Availability & Capacity
SQL Server: Always On send versus redo queues
A secondary falls behind and the team cannot tell whether transfer or replay is slow. Compare send queue, redo queue, throughput and replica connection state.
Environment and inputs: SQL Server operational monitoring; availability groups, SQL Agent and host-level metrics depend on edition, service and deployment.
Failure scenario
A secondary falls behind and the team cannot tell whether transfer or replay is slow. Confirm the cause before choosing a fix.
Evidence to collect
Compare send queue, redo queue, throughput and replica connection state. Record the time, affected scope and a healthy comparison interval.
Fix the confirmed cause
Investigate the stage accumulating work and test recovery after addressing that bottleneck. Write the expected result first. Change one relevant setting at a time.
Check the result and hand over
Repeat the check for always on send versus redo queues using the same scope and a representative interval. Check that the symptom is resolved, expected records are present and downstream results are correct. If coverage, correctness or latency worsens, restore the recorded configuration through the agreed rollback process.
Scope and precautions
Prefer read-only access and limit queries to the relevant period or dataset. This example has not been tested on your systems. Test changes in an approved environment. Keep credentials and sensitive data out of shared evidence.