Database Mirroring History


Applies To: SQL Server 2016

Use this dialog box to view the history of mirroring status for a mirrored database on a specified server instance.

To use SQL Server Management Studio to monitor database mirroring

Server instance
Name of the server instance from which the history is being reported.

Name of the database whose history is being reported.

Filter list by
Lists filter values. Choosing a new value refreshes the grid automatically.

The possible filter values are:

  • Last two hours

  • Last four hours

  • Last eight hours

  • Last day

  • Last two days

  • Last 100 records

  • Last 500 records

  • Last 1000 records

  • All records

Click to refresh the history list.

System_CAPS_ICON_note.jpg Note

This dialog box does not automatically refresh the history list. To refresh the list, either click Refresh or choose another filter option. Only members of the sysadmin fixed server role can update the mirroring history.

Displays the history list. Clicking on a column header sorts the grid by that column. The list contains the following columns:

Column nameDescription
Time RecordedTimestamp of the history row.
RoleCurrent mirroring role of the server instance for this database, either Principal or Mirror.
Mirroring StateState of the database:


Pending Failover




Witness ConnectionState of the witness connection in the mirroring session of the database, either Connected or Disconnected. If there is no witness, the value is NULL.
Unsent LogSize, in kilobytes (KB), of the unsent log in the send queue on the principal server instance.
Time to SendApproximate amount of time the principal server instance will require to send the log that is currently in the send queue to the mirror server instance (the send rate). Because the rate of incoming transactions can vary significantly, the time to send log is an estimate. However, the send rate can be useful for roughly estimating the time required for a manual failover.
Send RateRate at which transactions are being sent to the mirror server instance, in KB per second.
New Transaction RateRate at which incoming transactions are being entered into the principal's log, in KB per second. To determine whether mirroring is falling behind, staying up, or catching up, compare this value to the Time to Send value.
Oldest Unsent TransactionAge of the oldest unsent transaction in the send queue. The age of this transaction indicates how many minutes of transactions have not yet been sent to the mirror server instance. This value helps measure the potential for data loss in terms of time.
Unrestored LogThe amount of log waiting in the redo queue, in KB.
Time to RestoreApproximate number of minutes required for the log currently in the redo queue to be applied to the mirror database.
Restore RateRate at which transactions are being restored into the mirror database, in KB per second.
Mirror Commit OverheadAverage delay per transaction in milliseconds (only in synchronous modes). This delay is the amount of overhead incurred while the principal server instance waits for the mirror server instance to write the transaction's log record into the redo queue.

Start Database Mirroring Monitor (SQL Server Management Studio)
Monitoring Database Mirroring (SQL Server)
Start the Configuring Database Mirroring Security Wizard (SQL Server Management Studio)

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