Before You Begin

Before starting the upgrade procedure, read and follow the recommendations below:

To upgrade Veeam Backup Enterprise Manager to version 12.3, you must be running version 11a (build 11.0.1.1261) or later. To upgrade from earlier versions, contact Veeam Customer Support.
A machine on which you plan to install Enterprise Manager must meet the system requirements. For more information, see System Requirements.
A user account that you plan to use for upgrade must have sufficient permissions. For more information, see Permissions.
Backup infrastructure components communicate with each other over specific ports. These ports must be open. For more information, see Ports.
Check the Known Issues section of the Veeam Backup & Replication 12.3 Release Notes.
With Enterprise Manager and connected backup servers, remember to begin the backup infrastructure upgrade process with Enterprise Manager. Backup servers should be upgraded after that. When you use different versions of Veeam Backup Enterprise Manager and Veeam Backup & Replication, you may not be able to leverage all features of Veeam Backup Enterprise Manager. Moreover, data collection from backup servers of earlier versions takes more time, which can be critical if many backup servers are added to Enterprise Manager.

If you have a backup server installed on the same machine, upgrade it immediately after completing upgrade of the Enterprise Manager server. Otherwise, the Configuration Database Connection Settings utility will not work properly for Veeam Backup & Replication. For more information about the utility, see Configuration Database Connection Settings Utility.

In Enterprise Manager, you cannot edit jobs that are managed by backup servers with earlier versions installed until you upgrade the backup servers. Additionally, you cannot create and edit jobs of such backup servers in Veeam Self-Service Backup Portal for Cloud Director and vSphere Self-Service Backup Portal. For example, if you upgrade Enterprise Manager to version 12.3, you will not be able to edit jobs managed by a backup server with version 12.0 until you upgrade the backup server to version 12.3.
Upon the upgrade, the size of the Enterprise Manager configuration database may increase significantly. If your configuration database is based on Microsoft SQL Server Express Edition, ensure you are not about to exceed the database size limit of 10 GB. To prevent data loss, back up the configuration database before you upgrade Enterprise Manager.

Additionally, the size of Microsoft SQL Server transaction logs and the tempdb system database may grow. To avoid the overflow of the tempdb database, set the database to autogrow. After the upgrade is completed, you can shrink the files using Microsoft SQL Server tools.

Local antivirus or antimalware software can interfere with Enterprise Manager upgrade. If you receive the Failed to create website 0x80070020 message, disable your local antivirus or antimalware software and start the upgrade process again. You can re-enable your antivirus software once the upgrade completes. For more information, see this Veeam KB article.
.NET 3.5.1 WCF HTTP Activation Windows component prevents Enterprise Manager from functioning. Make sure there is no .NET 3.5.1 WCF HTTP Activation Windows component on the Veeam Backup Enterprise Manager server prior to the installation.