I am using Openfire-3.9.3 with RHEL 6. I am planning to upgrade my OS to RHEL 7.
Can someone advice me whether Openfire-3.9.3 is compatible with RHEL 7.
If you are able to install the same Java version, then i would guess it should work. But nobody here will tell you for sure. Not many RHEL users and 3.9.3 is 5 years old already. I think this version came with Java 7, not sure if it supported Java 8. I guess the only option to say for sure is for you to spin up a test machine with RHEL 7 and try to install 3.9.3 on it. Check if you can access Admin Console, setup a few test users and check connection from a client you are using.
It should work, but you would not want to use Java8, but stick with Java7.
We are running openfire 3.9.3 with Java version 8 in my redhat 6 machine. Shall i use the same Java 8 in my redhat 7 as well for openfire 3.9.3.
If it works correctly on the current system, then yes, you can use the same Java.