We have a requirement where we want to migrate BE data from one BE active space cluster to another active spaces cluster.

TIBCO BusinessEvents cluster migration to different environment depends on your persistence settings (persistent type).The deployment type like on-premise or containers or k8s cluster is not relevant to migrate the data from existing cluster to another environment.

When using Shared All persistence:

For persistence type shared all you just need to backup and restore the DB data to the new database in your new environment and update the JDBC resource before starting the agents in the new deployment.

When using Shared Nothing persistence:
You can copy the persistence store from current setup to the new one and restart the CacheServers with same member name as in the current environment.
The member name must match the existing one to be able to recover the data from persistence store. By default BE sets the membername to <hostname>.<agentname>. To guarantee that the member name is the same in the new environment set CDD property be.engine.cluster.as.hostaware.hostname.

Please refer to article https://support.tibco.com/s/article/Tibco-KnowledgeArticle-Article-43302 for complete details.

No Persistence

When persistence is not enabled you will lose the data when cluster is stopped. Here you can join the existing cluster from the new environment (if possible), wait until redistribution is finished and then stop the CacheServers in the existing system.