Off topic Increasing JVM heapsize is throwing errors

e-business 12.1.2 env
OS: Oracle Linux Server release 6.6
Linux xyz 2.6.32-300.32.3.el6uek.x86_64 #1 SMP Thu Sep 27 10:39:05 PDT 2012 x86_64 x86_64 x86_64 GNU/Linux

To address long garbage collection times and outofmemoryerrors trying to increase heapsize for JVM

There is 13GB free on the box before running below command:

top - 13:33:49 up 77 days, 4:33, 13 users, load average: 0.10, 0.08, 0.08 Tasks: 291 total, 1 running, 290 sleeping, 0 stopped, 0 zombie Cpu(s): 0.5%us, 0.2%sy, 0.0%ni, 99.2%id, 0.0%wa, 0.0%hi, 0.0%si,  0.0%st
Mem: 49559264k total, 36163844k used, *13395420k free*, 299616k buffers Swap: 18841520k total, 0k used, 18841520k free, 22636024k cached

free

             total       used       *free     *shared    buffers     cached
Mem:      49559264   36167308   *13391956       *1364     299616   22639036
-/+ buffers/cache:   13228656   36330608
Swap:     18841520          0   18841520

java -server -verbose:gc *-Xmx2048M -Xms2048M -XX:MaxPermSize=684M* -version java version "1.6.0_07"
Java(TM) SE Runtime Environment (build 1.6.0_07-b06) Java HotSpot(TM) Server VM (build 10.0-b23, mixed mode)

Even if we increase by 1M after this limit it throws errors:

java -server -verbose:gc -Xmx2048M -Xms2048M -XX:MaxPermSize=685M -version Error occurred during initialization of VM Could not reserve enough space for object heap *** glibc detected ***
/app/of1_dev/r12/apps/tech_st/10.1.3/appsutil/jdk/bin/java: free(): invalid pointer: 0xf7758250 ***

wondering why it is failing when there is free RAM available.

Thanks your your time.

Regards,
Sanjeev.

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