Monitoring SQL Server Database Mirroring with Email Alerts

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Problem

The number of Database Mirror pairs in our enterprise is increasing at an alarming rate. With the ease of setup, resilience and ability to seamlessly failover and failback, database mirroring has taken over from log shipping as the DR solution of choice. We need a basic script that we can execute on all servers participating in mirroring that will alert us if any Principals or Mirrors are in an abnormal state. The script needs to work on both Principal and Mirror server.

Solution

The Catalog View sys.database_mirroring contains one row for each database in the instance of SQL Server and also contains state information of all mirrored databases.  We'll query this Catalog View and raise an email alert for each mirrored database that we find in an abnormal state. We don't utilize a witness server in any of our mirrored pairs so we rely on manual failover.

Prerequisites

  1. A valid Database mail profile
  2. A valid login that has permission to send email i.e. a member of the DatabaseMailUserRole role in the msdb database
  3. At least one pair of mirrored databases to monitor

The Script

Substitute in the below script your Database Mail profile and a suitable email address to receive the alerts.

DECLARE @state VARCHAR(30) 
DECLARE @DbMirrored INT 
DECLARE @DbId INT 
DECLARE @String VARCHAR(100) 
DECLARE @databases TABLE (DBid INT, mirroring_state_desc VARCHAR(30)) 
 
-- get status for mirrored databases 
INSERT @databases 
SELECT database_id, mirroring_state_desc 
FROM sys.database_mirroring 
WHERE mirroring_role_desc IN ('PRINCIPAL','MIRROR') 
AND mirroring_state_desc NOT IN ('SYNCHRONIZED','SYNCHRONIZING') 
 
-- iterate through mirrored databases and send email alert 
WHILE EXISTS (SELECT TOP 1 DBid FROM @databases WHERE mirroring_state_desc IS NOT NULL) 
BEGIN 
   SELECT TOP 1 @DbId = DBid, @State = mirroring_state_desc 
   FROM @databases 
   SET @string = 'Host: '+@@servername+'.'+CAST(DB_NAME(@DbId) AS VARCHAR)+ ' - DB Mirroring is '+@state +' - notify DBA' 
   EXEC msdb.dbo.sp_send_dbmail 'valid_mail_profile', '[email protected]', @body = @string, @subject = @string 
   DELETE FROM @databases WHERE DBid = @DbId 
END 
 
--also alert if there is no mirroring just in case there should be mirroring :)
SELECT @DbMirrored = COUNT(*) 
FROM sys.database_mirroring 
WHERE mirroring_state IS NOT NULL 
IF @DbMirrored = 0 
BEGIN 
   SET @string = 'Host: '+@@servername+' - No databases are mirrored on this server - notify DBA' 
   EXEC msdb.dbo.sp_send_dbmail 'valid_mail_profile', '[email protected]', @body = @string, @subject = @string 
END

Practice

To verify the alert let's pause mirroring through the SQL Server Management Studio (SSMS). In Object Explorer right click your mirrored database > Properties > Mirroring option > Pause button as follows:

database mirroring status

Now, if the query finds a mirrored database in an abnormal state as shown below, it will send out an alert email alert:

database status

The script will also output the following information to notify you that an alert has been sent to be processed by Database Mail.

Mirroring Alert Message
-----------------------
Host: SERVERXXX.MirrorTest - DB Mirroring is Suspended - notify DBA
 
Mail queued.
 
 
Mirroring Alert Message
-----------------------
Host: SERVERXXX.sp_config_ssp2 - DB Mirroring is DISCONNECTED - notify DBA
 
Mail queued.

Email received that clearly shows the host name, database name and the abnormal state of the mirroring so that the DBA team can investigate further.

alert message
Next Steps


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About the author
MSSQLTips author Alan Cranfield Alan Cranfield is a versatile SQL Server DBA with over 10 years experience managing critical systems in large distributed environments.

This author pledges the content of this article is based on professional experience and not AI generated.

View all my tips



Comments For This Article




Monday, February 16, 2015 - 11:37:10 AM - Rajan Dubey Back To Top (36250)

how to implement this query for alert.


Friday, November 7, 2014 - 11:59:49 AM - smt Back To Top (35224)

Where should I execute the above code?


Monday, August 13, 2012 - 3:38:37 AM - Marko Schustek Back To Top (19016)

Thanks for that great Script. Saves me a lot of work!

Regards

 

Marko

 


Wednesday, March 21, 2012 - 2:36:08 PM - Laura Back To Top (16568)

In our company WMI is disabled and thus I cannot do anything through WMI.  I am trying to find examples of Mirror Alerts that do not use WMI.


Sunday, January 8, 2012 - 4:11:38 AM - Praveen Singh Back To Top (15543)

Hey Alan, thanks for your quick way to get the alert. I was wondering can I add multiple email addresses to receive the alert?


Thursday, October 15, 2009 - 12:10:55 PM - --cranfield Back To Top (4201)

yes, this tip is mentioned twice in my tip. Its a good one!


Thursday, October 15, 2009 - 12:08:17 PM - --cranfield Back To Top (4200)

Thanks for reading.  True, there are built-in alerts but they require some configuring and the document link you sent will show you how to do that.  I'm just showing DBAs another a way of configuring a quick dynamic alert when that all you need.

 Monitoring performance of your mirroring is a deeper subject.


Thursday, October 15, 2009 - 11:29:58 AM - admin Back To Top (4199)

Here is another tip that talks about using WMI as referred to in the above post

 http://www.mssqltips.com/tip.asp?tip=1564

 


Thursday, October 15, 2009 - 8:34:21 AM - ptheriaultdba Back To Top (4197)

While I agree with you that db mirroring must be monitored, I completely disagree with how your getting it done.  There are already built in alerts for this.  Just create an alert using WMI provider and you can query any state for the db mirror change.  Here is the link to how is should be done.  A DBA should also be looking for unsent and unrestored log thresholds...

http://technet.microsoft.com/en-us/library/cc966392.aspx

 Paul

http://forum.lessthandot.com/

 















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