How Heap memory impact when it increase


I’d like to thanks for giving me a opportunity to conversation with ignite team. currently i’m using openfire as my chat server which have 70000+ thousand users and in my project average rate of user registration is 1200 something. that’s why for scale purpose i need to increase heap memory as I show at admin console java memory has been used upto 97% .

So what’s impact can occurs …please explain me the pros and cons when it increased