Database Synchronization Status
Synchronized = Secondary Replicas has caught up. No Data Loss.
Synchronizing = Secondary Replicas is still catching up. Data Loss.
For Always On setup using “Asynchronous commit” Availability Mode, it is normal for the database to be in “Synchronizing” status.
For Always On setup using “Synchronous commit” Availability Mode, the database needs to be in “Synchronized” status.
Always On Dashboard
One of the easiest ways to monitor the status of an Availability Group, each of the replica servers, and the availability databases, is through the built-in dashboard in Management Studio. However, the default layout of the dashboard doesn’t provide a lot of details, and will need to be customized to show additional information about the replica servers as well as the availability databases. Additional columns can be added to the layout through the Add/Remove Columns link on the dashboard, or through the right-click context menu on any of the existing column headers, as shown below:
SSMS -> Always On High Availability -> Show Dashboard
File Bytes Received/sec
Amount of FILESTREAM data received by the secondary replica for the secondary database in the last second.
Log Bytes Received/sec
Amount of log records received by the secondary replica for the database in the last second.
Log remaining for undo
The amount of log in kilobytes remaining to complete the undo phase.
Log Send Queue
Amount of log records in the log files of the primary database, in kilobytes, that has not yet been sent to the secondary replica. This value is sent to the secondary replica from the primary replica. Queue size does not include FILESTREAM files that are sent to a secondary.
Amount of log records in the log files of the secondary replica that has not yet been redone.
Number of times the redo thread is blocked on locks held by readers of the database.
Redo Bytes Remaining
The amount of log in kilobytes remaining to be redone to finish the reverting phase.
Amount of log records redone on the secondary database in the last second.
Total Log requiring undo
Total kilobytes of log that must be undone.