Get-MailboxDatabaseCopyStatus Displays Incorrect Activation Preference Value

Current builds of Exchange Server 2013 and Exchange 2016 have a behavior in the Get-MailboxDatabaseCopy cmdlet that may cause an incorrect value to be returned for the activation preference of a database copy.

The bug is harmless to the operation of the database availability group (it will still use the correct activation preference values during BCSS), but if you’re relying on Get-MailboxDatabaseCopy to return those values in a script, or just during general admin, then you may be misled by the results.

Here’s an example. In this case I’ve used Set-MailboxDatabaseCopy to set each copy of the database DB02 to an activation preference of 4.

[PS] C:\>Set-MailboxDatabaseCopy DB02MELEX1 -ActivationPreference 4
[PS] C:\>Set-MailboxDatabaseCopy DB02MELEX2 -ActivationPreference 4
[PS] C:\>Set-MailboxDatabaseCopy DB02SYDEX1 -ActivationPreference 4
[PS] C:\>Set-MailboxDatabaseCopy DB02SYDEX2 -ActivationPreference 4

There are no warnings or other indications that it isn’t working, and Get-MailboxDatabaseCopyStatus shows me a result like this.

[PS] C:\>Get-MailboxDatabaseCopyStatus DB02 | select name,status,activationpreference | ft -auto

Name         Status ActivationPreference
----         ------ --------------------
DB02MELEX1 Healthy                    4
DB02MELEX2 Healthy                    4
DB02SYDEX2 Mounted                    4
DB02SYDEX1 Healthy                    4

Activation preference values are unique for each copy of a database, you can’t have an AP of 4 for every copy. And in this case I don’t, it is just the way the cmdlet works, because it queries the server instead of Active Directory (which is the authoritative source).

If I use Get-MailboxDatabase to query the AP instead I see the correct values.

[PS] C:\>Get-MailboxDatabase DB02 | Select -expandproperty:ActivationPreference

Key    Value
---    -----
SYDEX2     1
MELEX1     2
MELEX2     3
SYDEX1     4

And if I use the RedistributeActiveDatabases.ps1 script to rebalance the DAG it uses the correct AP values in doing so (truncated output here just to demonstrate the point).

-----------------------
Starting Database Moves
-----------------------

Considering move of 'DB02' from 'SYDEX2' (AP = 3) to 'MELEX1' (AP = 1)...
Database 'DB02' successfully moved from 'SYDEX2' to 'melex1'.

ServerName ActiveDbs PassiveDbs
---------- --------- ----------
MELEX1             2          2
MELEX2             1          3
SYDEX1             1          3
SYDEX2             0          4 `n

----------------
Summary of Moves
----------------
Successfully moved      : 1
Moved to less preferred : 0
Failed to move          : 0
Not moved               : 3

DbName                    : DB02
ActiveOnPreferenceAtStart : 3
ActiveServerAtStart       : SYDEX2
ActiveOnPreferenceAtEnd   : 1
ActiveServerAtEnd         : melex1
IsOnMostPreferredCopy     : True
MoveStatus                : MoveSucceeded

When I originally wrote this article, I referred to this behavior as a bug, because that’s what was confirmed to me. Since then, a Microsoft engineer has clarified why this behavior is expected, and is not considered a bug. It isn’t a serious issue, as long as you’re aware of it and use the Get-MailboxDatabase cmdlet to verify your AP values are correct.

Updated: 22nd June, 2016