DHIS2- TompCat Issue(Java heap space) caused by out of memeory error

I’ve been trying to export to do backup of work done and replicate the work on a different server and I’ve been running into HTTP Status 500 - Internal Error Server saying java heap space memory…

How could you identify it was a firewall issue? I’m on a 16GB RAM and Java 1.8 with OPTS being at 4000 and 7000 as recommended in the documentation.