Develop Reference

Setting heap size in Java

I am trying to run a Java tool in Linux Ubuntu system and I keep getting the following error after the program imports 12% of the data:
Fata Error:
Exception in thread 'Thread-l" java.lang.OutOfMemoryError: java heap space
I tried to set the heap size using
java -Xms8G -Xmx16G -jar Haploview.jar
but the error appears again exactly at same point after just using less than 500M Of the allocated Ram.
Using the command 'free -m' I can see that there are lots of free RAM memory left but I don't know why Java do not use it

According to the specification Haploview allocates 512 MB of memory by default. You can increase the memory up to 2000 MB via java -jar Haploview.jar -memory 2000.
For details see https://www.broadinstitute.org/haploview/frequent-questions
But a memory larger than 2 GB is most likely not possible because Haploview seems to be a 32-bit application which is limited to a memory
of 2 GB independent of the underlying OS (32 Bit or 64 Bit).
See https://haploview.software.informer.com/download/
and Memory limit to a 32-bit process running on a 64-bit Linux OS

Maximum Heap Size of java is too small

I am using a 64 bit Windows 10 system with 32Gb of RAM. One of my 32 bit java application requires a lot of memory so I decided to change the minimum heap size to -Xms4096m at the runtime parameter field in the java configuration dialogue.
However, I soon realised that it would not do anything because apparently my system's maximum heap size is only 247.50mb (which is way too small for a 64 bit system). I am using a 32 bit java so I am expecting a max heap size of around 4GB. Can anyone tell me what determines the maximum heap size and how do I change it?
UPDATED: I understand that the maximum I can allocate is 2GB for a 32 bit system. So my question now is how come for my system, its only 247.50mb?
BELOW ARE MY Java Settings:

Max Heap memory single process allowed to use for a given ram size?

Heap is part of RAM.But still there is a limit that we can not define heap size beyond some percentage of RAM.For example:- i have 32 bit winodws xp OS and 4
GB RAM. But i can not declare the heap size more than 1600 MB. My question here why we can not declare heap size to some large value say 3GB which
is lower than my 4GB RAM(as in 32 Bit can ustilize up to 4gb of RAM)? This is true for single process.
I mean i can start two tomcat or any other java process
allocating 1600MB heap size to each but i can not allocate 3200MB to single process.what is the reason that behind that?

32-bit windows only allows 2GB of address space to a single process (without special extensions enabled.) The OS keeps the other 2GB for itself. Then on top of that Heap is not all of the memory that JVM needs. There is permgen space, and the memory that the code of the JVM itself uses.

If its not 64 bit 4GB cannot be allocated.

Unable to set Java heap size larger than 1568

I am running a server with the following attributes:
Windows Server 2008 R2 Standard - 64bit
4gb RAM
I am trying to set the heap size to 3gb for an application. I am using the flags -Xmx3G -Xms3G. Running with the flags results in the following error:
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.
I have been playing with the setting to see what my ceiling is and found that 1568 is my ceiling. What am I missing?

How much physical memory is available on your system (out of the original 4 GB)? It sounds like your system doesn't have 3GB of physical memory available when the vm starts up.
Remember that the JVM needs more memory than is allocated to the heap -- there are other data structures as well (thread stacks, etc) that also need memory. So the settings you are providing attempt to use more than 3GB of memory.
Also, are you using a 64-bit jvm? The practical limit for heap size on a 32-bit vm is 1.4 to 1.6 gigabytes according to this document.

Java requires continuous virtual memory on startup. On windows, 32-bit application run in an 32-bit emulated environment so you don't get much more continuous memory than you would in a 32-bit OS. c.f. on Solaris you get over 3 GB virtual memory for 32-bit Java.
I suggest you use the 64-bit version of Java as this will make use of all the memory you have. You still need to have free memory but the larger address space doesn't suffer from fragmentation.
BTW: The heap space is only part of the memory used, you need memory for shared libraries, direct memory, GUI components etc.

It seems you don't have 3G of physical mememory available. Here is an interesting article on Java heap size settings errors. Java heap size setting errors

Avoiding Initial Memory Heap Size Error

I run a Java code with the following command:
$ java -Xms4G -Xmx4G myjavacode
My cpu's RAM capacity is 6GB.
However it always fail to execute giving me this
error message:
Invalid initial heap size: -Xms5G
The specified size exceeds the maximum representable size.
Could not create the Java virtual machine
Is there any way to set up Java option so that we can
execute the code?

You've exceeded the maximum heap size of your JVM. This is both JVM and OS dependent. In most 32-bit systems the maximum value will be 2Gb, regardless of the physical memory available.

By default Java will run in 32 bit mode. Be sure to give it the -d64 option to put it into 64 bit mode. Once in 64-bit mode, you shouldn't have any trouble allocating a 6GB JVM.

Actually, the maximum memory size on 32-bit systems can vary, being anything up to 4 GB, but 2 GB is a common value. It's often possible to re-link your kernel to increase this to 3 or 3.5 GB. The issue, of course, is that you just don't have the address space to map more memory. Have you tried a 64-bit machine?
Also, remember to set your ulimit higher before you do this.