My understanding is that the java virtual machine on windows does a VirtAlloc() call to get memory for its heap.
I am running the 32 bit version and sometimes it fails to get the 1G of heap that it needs.
For some reason this varies based on what else is running on this Windows 7 workstation even though it has plenty of memory overall.
Example using java -Xms... -version
c:\Program Files (x86)\Java\jre7\bin>java.exe -Xmx1024m -version
Error occurred during initialization of VM
Could not reserve enough space for object heap
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.
c:\Program Files (x86)\Java\jre7\bin>systeminfo
...
Total Physical Memory: 16,308 MB
Available Physical Memory: 13,108 MB
Virtual Memory: Max Size: 32,614 MB
Virtual Memory: Available: 29,291 MB
Virtual Memory: In Use: 3,323 MB
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Plenty of memory and yet the call fails. Closing a large application like MS Outlook (not even Java) allows the command "java.exe -Xmx1024m -version" to work.
thank you