Increase heap size in Java

java heap-memory
Sunil picture Sunil · Oct 14, 2009 · Viewed 761.5k times · Source

I am working on a Windows 2003 server (64-bit) with 8 GB RAM. How can I increase the heap memory maximum? I am using the -Xmx1500m flag to increase the heap size to 1500 Mb. Can I increase the heap memory to 75% of physical memory (6 GB Heap)?

Answer

Steve B. picture Steve B. · Oct 14, 2009

You can increase to 4GB on a 32 bit system. If you're on a 64 bit system you can go higher. No need to worry if you've chosen incorrectly, if you ask for 5g on a 32 bit system java will complain about an invalid value and quit.

As others have posted, use the cmd-line flags - e.g. 

java -Xmx6g myprogram

You can get a full list (or a nearly full list, anyway) by typing java -X.

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