Best practices for upgrading from the embedded database to the Microsoft SQL Server Express database

In 14.3 RU1, the default database that is installed with
Symantec Endpoint Protection Manager
(SEPM) changed from the embedded database to the Microsoft SQL Server Express 2017 database. When you upgrade or install the management server for the first time using the default configuration in the Management Server Configuration Wizard, the SQL Server Express database is installed automatically and replaces the embedded database.
When you upgrade to version 14.3 RU1 or later, the management server computer must fulfill certain requirements, or the management server upgrade cannot proceed. The Management Server Configuration wizard informs you if you encounter these issues and gives you the opportunity to fix them.
Things to know before you upgrade
Before the upgrade, check the following issues that you may need to fix before you install.
Fixing issues before upgrading
Issue
Description
Insufficient database size
The SQL Server Express database has a maximum capacity of 10 GB for data files and log data. The Symantec Endpoint Protection Manager makes a backup of the embedded database before the installation starts. If that backup is larger than 10 GB, the upgrade cannot continue. You must reduce the amount of data either before you start the upgrade or during the upgrade. The Management Server Configuration wizard informs you when the database size is too large.
If the database is over 10 GB before you start the installation, perform the following tasks:
Both the Microsoft SQL Server Express database and the Microsoft SQL Server database use a feature called FILESTREAM to reduce the database size. If you find out that the database size is too large or close to too large during the upgrade, you can perform the following actions:
If you use the SQL Server database, periodically check the database size to make sure that the database does not reach its maximum size. See:
Increasing the Microsoft SQL Server database file size
Insufficient disk space
Ensure that there is a minimum of 10 GB of available disk space on the management server computer to perform the upgrade.  See:
The Symantec Endpoint Protection Manager does not communicate with the database
Symantec Endpoint Protection Manager uses a certificate to authenticate communications between the
Symantec Endpoint Protection
(SEPM) and the Microsoft SQL Server Express or SQL Server databases. You must generate the certificate and import it into the
Symantec Endpoint Protection Manager
computer for SEPM to connect to either the SQL Server database. If the certificate does not exist, is expired, or is about to expire, the connection between SEPM and the database fails.  See:
To check that the management server connects to the database, see:
Troubleshooting issues with upgrading to the Microsoft SQL Server Express
You may have one of the following issues when you upgrade:
More information