[keycloak-user] What is the procedure for upgrading from 2.x to 3.x and beyond?

We are planning on using keycloak for SSO for our entire organization. We plan on running all of Keycloak in either Azure or AWS using a hosted SQL database (MS SQL or Postgres), and having multiple keycloak VMs which will connect to the single database instance. I have already figured out jdbc_ping and its configuration in terms of caching, etc. What we would like to know though is when we deploy the servers, what happens when we upgrade from whatever version we decide to implement to a later version of Keycloak? Are there database schema updates that happen in the background? Do we need to shut down the entire system, then start a new version and let it migrate? Can a newer and older version of Keycloak be connected to the same database or is that an invalid use case? So bottom line: We need to know the upgrade procedure when running a very large installation of Keycloak with multiple VMs as the Keycloak servers. Thank you. This message is the property of CARBONITE, INC. and may contain confidential or privileged information. If this message has been delivered to you by mistake, then do not copy or deliver this message to anyone. Instead, destroy it and notify me by reply e-mail