Arcadia visualization server stores application metadata in a DB. By default it’s stored in sqlite but in most production deployments it’s highly recommended to use a proper load balanced RDBMS like mysql or oracle.
You can configure this during the installation. For example let’s say you are using MySQL.
The default port for mysql is 3306. Unless you are using a custom install/configuration, that’s usually what I have seen.
Inside Ambari (or Cloudera Manager), under Arcadia service configuration, you have the flexibility to specify the port used to connect to the RDBMS as required by network security policy. So you want to make sure your network security has the configured firewall to have that port open.
See screenshot below.