In SQL Server Management Studio, Right click principle database -> properties -> Mirroring, the click Resume button. The alternative way is to right click principle database -> Tasks -> Mirror, the click Resume button.
We can also run the following Transact-SQL query to resume the database mirroring:
ALTER DATABASE userdb SET PARTNER RESUME;
To check the synchronizing progressing by running following Transact-SQL query:
SELECT [counter_name] as CounterName,[cntr_value] as CounterValue FROM sys.dm_os_performance_counters WHERE [object_name] LIKE ('%Database Mirroring%') AND [counter_name] IN ('Log Send Queue KB','Redo Queue KB') AND [instance_name]='TESTDB'; CounterName CounterValue Redo Queue KB 1260219 Log Send Queue KB 8407945
“Redo Queue KB” : Logs to applied onto mirroring database.
“Log Send Queue KB” : Logs to be sent to mirroring database.
Another alternative way to check mirroring status and statistics:
Right click principle database -> Tasks -> Launch Database Mirroring Monitor.
Click History, you can find when the mirror broke: