Sean's Musings as a Service

Sean's Musings as a Service

What is the largest max heapsize for a 64 bit IBM JVM?

  • Published:
  • categories: ibm
  • tags: heapsize, ibm, java, jvm, memory

Looking for something like a technote I found for 32 bit Windows 1. But I was hoping for a more generic answer that I could reference to clients at when I offer WAS JVM settings to give them a sigh of relief that I am in fact not crazy. So I started poking through the IBM JVM docs and found this 2 stating the upper limit is 16 exabytes and FYI google tells me 3 that is a lot.

1 EB = 1000000000000000000B = 1018 bytes = 1073741824 gigabytes = 1048576 terabytes4

1EB x 16 = 1,073,741,824 GB

With that said, my recommendation for a 8-16 GB JVM max heap size recommendation doesn’t even sound like that much. But still have a bit more digging to get my head around some actual tuning and monitoring of the JVM for WebSphere