JVM max heap size on 32-bit platform for WebSphere Portal

Maximum JVM heap size for 32-bit platform can be set from 1.5-2 GB. But mostly the optimum value is about 1280 MB.

It turns out that memory locations in a 32-bit system are referenced by 32-bit unsigned integers. This allows up to 2^32 possible memory locations. Since each location stores 1 byte you get 2^32 bytes or 4 GB if you prefer. On a 64 bit system there are 2^64 locations, or 16 exabytes.

Now, in Windows, the contiguous part becomes a big issue, but that is just how Windows does things. The idea is that you need to have an entire “uninterrupted” range for your heap. Sadly, Windows allocates some memory somewhere in the middle. This basically leaves you with about half the left side or half the right side, about 1.5-2GB chunks, to allocate your heap.

References:

http://stackoverflow.com/questions/2457514/understanding-max-jvm-heap-size-32bit-vs-64bit

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About Ishtiaque

I am IBM Certified Infrastructure Systems Architect, TOGAF 9 Certified, ITIL V3 Foundation certified and Oracle Certified Export in Java Web Component Developer with over 10 years of support and development experience in IBM middleware software and Java. Additionally, have a sound grip in databases, Linux and OpenStack administration. I hold the following certifications: IBM Certified Infrastructure Systems Architect TOGAF 9 Certified Oracle Certified Expert, Java EE6 Web Component Developer Oracle Certified Professional – Java 6 Programmer ITIL v3 Foundation Certified IBM Certified Solution Architect – Cloud Computing Infrastructure V1 IBM Certified System Administrator – WebSphere Portal V8, V7, V6.1, V6 IBM Certified System Administrator – WebSphere Application Server V7, V6.1 IBM Certified System Administrator – AIX V7 IBM Certified System Administrator – WebSphere MQ V7 IBM Certified Deployment Professional – Business Process Manager Advanced V7.5 IBM Certified Solution Advisor – Cloud Computing Architecture V3 IBM Certified Solution Developer – WebSphere Portal V5.1
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