How much heap should be allocated to a Java instance?

Issue

• With memory well in excess of 10G, on a 64-bit system, how much memory should be allocated to the JVM heap. Should all of it be allocated to the heap?
• What JVM heap size or settings are recommended for a 32-bit system?
• Are there any limitations to set max heap size of JVM? What are the max values that we can use?
• How much RAM should I allocate for JBoss running on Windows 2008?
• I want to know how much memory I can allocate to a container in JBoss Fuse Fabric. For example, I modified the "instance.properties" -Xms1024m -Xmx2048m, and it run without any
  problem. But I need to allocate more memory, so can allocate 10GB or something for Xmx? I am running Red Hat 6 on 64-bit
• We are using JBoss Fuse to create and manage a network of 8 brokers. We used the stock settings released with JBoss Fuse/ActiveMQ to configure the brokers.
  we have not touched the runtime environment settings for ActiveMQ. We are using 64-bit processing with over 10GB of RAM. I believe the standard JVM settings are 512MB for the AMQ brokers, so before we begin modifying these settings, we are asking if there are some recommended settings for JBoss Fuse ActiveMQ brokers on a 64-bit CPU. Can you give us some guidance on what would be some settings?
• We have a server with 48 GB RAM on which we deployed to run 4 instances of JBoss SOA 5.3.1?
• We have an ear file which is working on client desktop that needs to run on a new JVM on JBoss 5.1.0. Could you please guide us the steps involved in the configuration: Building the new JVM for new EAR file.
• How much memory should I allocate to Red Hat Single Sign-On?