I am preparing to upgrade OpenDJ directory server 3.5 to DS 6.5, which is a supported version according to the documentation.
OpenDJ includes config store and CTS.
OpenDJ is set as Session Failover (4 servers)
I will also upgrade the Operating System from RedHat to Ubuntu (new server)
please make a step-by-step recommendation on how to upgrade
I am sorry for my English
I don’t think that moving from RedHat OS to Ubuntu should be considered as an “upgrade”. It’s a migration…
Now since the new OpenDJ instances will be installed on a new server, this is not really a OpenDJ upgrade either.
I would suggest that you install a new server with the DS 6.5 server, configure that DS instance like all existing ones, then add it to the replication topology and initalize the data (using backup/restore or dsreplication initialize, depending on the size of data or your need to change the default database indexes).
Replication is designed and has been tested to work across versions of OpenDJ/ForgeRockDS, from 2.6 all the way to the latest version aka 6.5.2).
Once the new server is replicating with the 4 existing one, you can start adding new servers the same way and removing the old ones one by one (first unconfigure replication on the old server and then stop it forever).