Exchange Server - Namespace DAG Status

The Namespace DAG Status section reports the health of a Database Availability Group. Five monitoring tests are presented under it:

• Database Copy Health Status — the health of individual database copies, and their copy and replay queue lengths. Covered in detail on this page.
• Fail Over State — whether a server or its databases have failed over to a copy.
• Active Preference — whether active copies are sitting on their preferred servers.
• Database Redundancy — how much redundancy remains across the DAG.
• Replication Health and Network Health — the replication pipeline and the DAG networks it runs over.

Each has its own page in the MailscapeWeb interface, listed at the end of this article.

Database Copy Health Status

Three test results are displayed through this page:

• DAG Database Copy Status
• DAG Database Copy Queue Length
• DAG Database Replay Queue Length

The data shown is drawn from the Functionality Agent results. The XML node inspected is LogReplication, in:

LogFiles\<server>\FunctionalityAgentMessage.xml

The page itself can be opened directly on the ENow web server:

http://localhost:20080/MailscapeWeb/DAG/DAGDatabaseCopy.aspx?server=<SERVER>

Replace localhost with the web server's host name if you are browsing from elsewhere, and 20080 with your own port if it was changed during installation.

To confirm the result from the Exchange Management Shell:

Get-MailboxDatabaseCopyStatus

DAG Database Copy Status

The database copy status maps to a dashboard indicator as follows.

Content Index State

The Content Index State returned by the Functionality Agent is also folded into the status calculation, unless the database has been excluded from that consideration in the Admin Console.

The Content Index State result is merged with the database status result to produce the overall status for the copy.

Alerting

Alerts are generated for the following conditions:

• Critical — the database status is one of the red values above, or the status is unknown or otherwise not recognised.
• Critical — Content Index State is included in the calculation and its value begins with Failed.
• Warning — Content Index State is included and its value begins with Crawling or Unknown. If the overall status is already critical, a critical alert is sent instead.

Note that warning alerts relate to Content Index State only. The database copy status itself raises a critical alert or none.

Queue lengths

• DAG Database Copy Queue Length uses the CopyQueueLength XML attribute, compared against the threshold configured in the Admin Console.
• DAG Database Replay Queue Length uses the ReplayQueueLength XML attribute, compared against the threshold configured in the Admin Console.

Because both are threshold-driven, confirm the values in force in your own console before treating a warning or error as unexpected.

Fail Over State

Detects whether any server in the DAG, or any of the databases on it, has failed over to a copy. This reports a change of state rather than a threshold, so there is nothing to tune — the alert is "The DAG Failover state has changed".

See Exchange Server - Namespace DAG Status - Fail Over State for the full article.

Active Preference

Reports whether active database copies are running on their preferred servers. After a failover, Exchange does not return copies to their preferred host automatically, so this is what tells you the environment is still unbalanced once the original fault is fixed.

To validate the result, open the Exchange Management Shell on one of the Exchange servers and run:

cd $exscripts
.\RedistributeActiveDatabases.ps1 -DagName "<your DAG name>" -ShowDatabaseCurrentActives

The output shows which server currently hosts each active copy, and will align with what the monitoring page presents.

Database Redundancy

Reports how much redundancy remains across the DAG — that is, whether each database still has the number of healthy copies it is supposed to have.

To validate the result, open the Exchange Management Shell on one of the Exchange mailbox servers and run:

cd $exscripts
.\CheckDatabaseRedundancy.ps1

The output will align with what the monitoring page presents.

Replication Health

Reports the health of the replication pipeline between DAG members. To validate the result, run the following from the Exchange Management Shell on the affected server:

Test-ReplicationHealth

Network Health

Reports the state of the networks the DAG uses for replication and for client traffic. Open the monitoring page listed below for the detail behind the indicator.

To inspect the DAG networks directly in Exchange, Get-DatabaseAvailabilityGroupNetwork returns the configured networks and their current state.

Monitoring page URLs

All paths are relative to http://localhost:20080/, served by the ENow web server. Replace localhost with the web server's host name if browsing from elsewhere, 20080 with your own port if it was changed at installation, and <SERVER> with the monitored server you are investigating.