#1. The OCI Java client uses a lot of the same technologies that a RAU uses to speak to the OCI operational server - same DNS dependencies, etc.
Have you recently uipgraded OCI?
When you upgrade OCI versions, it is best to:
Ensure the Java cache is emptied on client workstations
Ensure you are running the appropriate Java version - OCI 7.2.x requires Java 8 at a minimum. I think there is a floor for Java 8 support, but I don't have the specific minimum build number.
General Java client thoughts:
Java runtimes may default to observing the operating systems Internet proxy settings - this can be problematic, so you may need to go into the Java control panel icon, and disable the proxy stuff
I would clear the Java cache, check the proxy, and look at:
c:\users\%username%\sanscreen-client.log
After I try running the client again
#2. Yes, if there is a firewall between the DWH reporting portal users and the OCI 7.2.x DWH, you will want a firewall exception to allow them to access tcp 9300