Hi,
can we export database of PRD and import in some other system and make that system as PRD
Yes you can export the database of PRD and import the same to other system,but as per my understandings you are going to use two PRD server at your end,one is for the upgrade process from EHP4 to EHP6 and other is for regular activities of production.Please confirm ?
we can keep app server down once update done with EHP6 then again restore this database to original server
As per your scenario all production users will work on the standby server which you made for the time being,here the main gap comes as you are upgrading the other system and users are working on other standby,so database gaps will come in seen.Database export import will not be beneficial for you after one system upgraded and with system on live production users are working.
It would be better to opt sufficient hardware resources for Production system.
Please correct me if i misunderstand your question and elaborate as per you.
Regards,
Gaurav