Exchange 2019 duplicate database - database CNF:GUID

Abdulrahman Alsowaina 21 Reputation points
2021-10-17T06:42:48.867+00:00 
 We are migrating from Exchange 2019 to 2019. Today we noticed there are duplicate databases in Exchange Control panel (on Exchange 2019). the databases have the same name as the current database except for an appended CNF:GUID at the end.

For example:
(this is a database in 2019 server that is part of a DAG)

Name : 2019DB01
DatabaseSize : 31.13 GB (33,420,214,272 bytes)

(there is a duplicate database that is visible on Exchange control panel and Exchange Management Shell)

Name : 2019DB01
CNF:eag4m3s405-6c73-365d-bc306-c3po82f204863c
DatabaseSize :

the duplicate databases are in a duplicate DAG. the DAG and databases were created after installation, they were later removed and recreated using the same name.

When I search for the CNF database using the shell

get-mailbox -Database 2019DB01CNF:eag4m3s405-6c73-365d-bc306-c3po82f204863c | select name

I get the following error:

Couldn't find database "2019DB01CNF:eag4m3s405-6c73-365d-bc306-c3po82f204863c". Make sure you have typed it correctly.

Is it safe to delete the duplicate database/DAG through Exchange control panel or ADSI Edit ?
Would this cause any issues related to Client connectivity ?
Should we pause the migration until this issue is resolved ?

Thank you.

Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Joyce Shen - MSFT 16,641 Reputation points
    2021-10-18T02:07:01.65+00:00

    Hi @Abdulrahman Alsowaina

    For various reasons, there are times when Active Directory may encounter a situation where multiple objects appear. The duplicates will be named with a CNF:[GUID] on the end of the name.

    To resolve this issue, like you said, we could remove the duplicate object in ADSIEDIT. Note that please backup the AD first before performing the operation.
    In addition, you could also check if any related error logs recorded in event viewer which lead to this issue.

    Below is a thread discussed about the similar issue for your reference: Duplicate Server Name in DAG Database Management

    How's your migration going now? Here is a link introduces about the migration of dag in exchange server, you could refer to the steps introduced in it.(Also applicable to exchange 2019)
    Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

    1) Create the new Exchange 2019 DAG and add Exchange 2019 mailbox servers to the DAG
    2) Move mailboxes from databases in the old Exchange 2019 DAG to the new Exchange 2019 DAG
    3) Create mailbox database copies within the new Exchange 2019 DAG
    4) Remove the database and its copies from the old Exchange 2019 DAG
    5) Remove the old Exchange 2019 DAG members and the DAG itself – either in GUI or by running Remove-DatabaseAvailabilityGroup cmdlet
    6) Reconfigure DNS, Autodiscover …

    If an Answer is helpful, please click "Accept Answer" and upvote it.

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  1. Abdulrahman Alsowaina 21 Reputation points
    2021-10-18T06:07:18.467+00:00

    Hi @Joyce Shen - MSFT

    Thank you for your reply, the migration is going smooth so far.
    We had some issues during Exchange 2019 deployment (DAG wasn't configured properly due to network issues)
    We've removed the old DAG and the old databases, then we configured a new DAG and added the databases.
    We tested the client connectivity and mail flow, once we confirmed everything is working on new Exchange 2019 we started migrating the users.

    We've migrated a little over half of the users.
    Yesterday, we noticed the old DAG and databases (previously deleted) are present on Exchange server.
    The old databases have the same name as the new databases.

    Do we need to deconfigure the new working DAG and configure a new one, or we can just simply delete the CNF:GUID databases ?

    Regards,