With Azure DevOps 2019, Microsoft renamed Visual Studio Team Foundation Server to Azure DevOps Server and Visual Studio Team Services(VSTS) to Azure DevOps Services.

Now due to this similar naming people often gets confused. So lets understand this in simple words,

1. Azure DevOps Server is the on-premises offering. It is a new release of Team Foundation Server 2018.
2. Azure DevOps Services is the cloud offering. It is a new name given to Visual Studio Team Services.

In this article we will discuss how we can update our on-premises TFS Server to Azure DevOps Server. Lets begin!

• Download the latest version of Azure DevOps Server here.

• Install downloaded setup.
  

• Once installation is complete. Configuration wizard will appear on the screen. Here it will ask for a deployment type, as we are updating the release version, select option "I have an existing database to use for this Azure DevOps Server deployment".
  

• Now configuration wizard will show the databases tab. Here we will take a backup of the existing database. It is important, if something goes wrong we can restore these backups and roll back to our previous version of TFS.
  

• Select databases which you want to backup and click on "Backup Now".
  

• After database backups, we will choose our deployment scenario. Select "Production Upgrade" and click on the next button.
  

• On the account tab we will setup a user account from the given options. You can use your existing user.
  

• In the application tier tab will show the existing site configuration. We can make changes if we want to otherwise just click on next.
  

• If our existing on-premises server has some Search configuration settings you can configure them now.
  

• After this configuration wizard will ask to review your configuration.
  

• Once reviewed, click on the configure button.
  

• After the configuration process finishes, click on the next button.
  

• Once the configuration process gets complete. It will show a success message.
  

• Review the results and click on next.
  

We have successfully updated to the Azure DevOps Server 2019.

Note: In case you want to rollback to previous version perform below steps,

1. Uninstall Azure DevOps Server 2019.
2. Restore the database backup on database server which we took in the beginning of the process.
3. Now just install TFS 2018 again and select existing database option and your good to go!

I hope this will be helpful!