There currently isn't any official documentation for upgrading Crowd Data Center

Installation and Upgrade Guide only covers upgrading for server

Upgrade guide should specifically include removing the openidserver.xml file for the other nodes, per Upgrade from Crowd Server to Crowd Data Center

Go to <installation-directory>/apache-tomcat/conf/Catalina/localhost, and delete the openidserver.xml file. This is needed because currently the CrowdID component doesn't support clustering, and it must be enabled only on the first node. The component will work as usual.