We are going through a situation where current NAM server resources are not sufficient to handle the load (especially memory), hence, we want to bring it up another server to overcome.
What points should be considered, for this type of migration without losing any data?
The best way to scale your NAM Server is to do horizontally by adding additional server(s) as node server(s) and creating (or extending an existing) NAM server load-balancing cluster.
The historical data will be preserved in the existing server and only new data will be balanced across the additional node server(s).
Please continue working on this with Support in JIRA ticket. Forum is not the best place to troubleshoot individual problems, especially since you already have opened a support ticket. It's possible to setup a new NAM server installation on another machine, then copy \config\repository.properties file from the old server and the content of \classes\CustomQueries\ folder (patches, if any) and this will allow to connect to the same DB. It is mandatory to have the old server stopped entirely before you attempt to connect to the same database from another NAM server instance/server.