Develop Reference

Java Heap space issue while executing .jar file from the command prompt [duplicate]

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)?

You can increase to 2GB 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.

It is possible to increase heap size allocated by the JVM by using these command line options:
-Xms<size> set initial Java heap size
-Xmx<size> set maximum Java heap size
-Xss<size> set java thread stack size
In the following example, minimum heap size is set to 16mb, and the maximum to 64mb:
java -Xms16m -Xmx64m ClassName

On a 32-bit JVM, the largest heap size you can theoretically set is 4gb. To use a larger heap size, you need to use a 64-bit JVM. Try the following:
java -Xmx6144M -d64
The -d64 flag is important as this tells the JVM to run in 64-bit mode.

You can increase the Heap Size by passing JVM parameters -Xms and -Xmx like below:
For Jar Files:
java -jar -Xms4096M -Xmx6144M jarFilePath.jar
For Java Files:
java -Xms4096M -Xmx6144M ClassName
The above parameters increase the InitialHeapSize (-Xms) to 4GB (4096 MB) and MaxHeapSize(-Xmx) to 6GB (6144 MB).
But, the Young Generation Heap Size will remain same and the additional HeapSize will be added to the Old Generation Heap Size. To equalize the size of Young Gen Heap and Old Gen Heap, use -XX:NewRatio=1 -XX:-UseAdaptiveSizePolicy params.
java -jar -Xms4096M -Xmx6144M -XX:NewRatio=1 -XX:-UseAdaptiveSizePolicy pathToJarFile.jar
-XX:NewRatio = Old Gen Heap Size : Young Gen HeapSize (You can play with this ratio to get your desired ratio).

It is possible to increase heap size allocated by the JVM in eclipse directly
In eclipse IDE goto
Run---->Run Configurations---->Arguments
Enter -Xmx1g(It is used to set the max size like Xmx256m or Xmx1g...... m-->mb g--->gb)

java -d64 -Xms512m -Xmx4g HelloWorld
where,
-d64: Will enable 64-bit JVM
-Xms512m: Will set initial heap size as 512 MB
-Xmx4g: Will set maximum heap size as 4 GB
(here java file name is : HelloWorld.java)

Please use below command to change heap size to 6GB
export JAVA_OPTS="-Xms6144m -Xmx6144m -XX:NewSize=256m -XX:MaxNewSize=356m -XX:PermSize=256m -XX:MaxPermSize=356m"

Can I increase the heap memory to 75%
of physical memory(6GB Heap).
Yes you can. In fact, you can increase to more than the amount of physical memory, if you want to.
Whether it is a good idea to do this depends on how much else is running on your system. In particular, if the "working set" of the applications and services that are currently running significantly exceeds the available physical memory, your system is liable to "thrash", spending a lot of time moving virtual memory pages to and from disk. The net effect is that the system gets horribly slow.

Several people pointed out the specific answers for heap size with the jvm options of -Xms and -Xms. I want to point out that this is not the only type of memory options for the jvm. Specifically if you are get stack over flows, then you'll want to increase the size of the stack by adding an additional option like -Xss8m.
For this problem, the jvm options of something like -Xms2g -Xmx6g -Xss8m would be a solution.
I'm sharing this information as my google searches on how to increase jvm memory took me to this solution, and the solutions didn't work with high amounts of memory allocation. Once I figured out what the specific settings were for, I was able to google how to increase the stack size and found the missing param. :) Hope this saves others time, as it would of saved me a ton of time. :)

This only works with 64 bit version of Java. Go to Control Panel and click on the Java icon. On the small window of Java Control Panel, click on the Java menu bar and then click on view button.
If you have two Java platforms, disable the previous version of Java, then click on Runtime parameters text field and write -Xmx1024m or less than RAM size. Don't increase heap size equal to RAM otherwise your system will crash.

Yes. You Can.
You can increase your heap memory to 75% of physical memory (6 GB Heap) or higher.
Since You are using 64bit you can increase your heap size to your desired amount. In Case you are using 32bit it is limited to 4GB.
$ java -Xms512m -Xmx6144m JavaApplication
Sets you with initial heap size to 512mb and maximum heapsize to 6GB.
Hope it Helps.. :)

I have problem running the py files in my java code using eclipse/STS, getting PyException due to insufficient jvm heap memory. I have done the changes as mentioned below and I'm able to resolve this issue. Below is my System configuration.
And these are the changes I did in my workspace and voila it runs perfect now.

Here are the steps if someone wants to know how to do this in windows.

will java use more memory when running on machine with larger ram

If I have a smaller-ram machine and a larger-ram machine. I run the same java code on them.
Will jvm do garbage collection more lazily on the machine with larger ram?
The problem I am trying to solve is an out of memory issue. People reported that they have Out of memory issue on small ram machine. I want to test that but the only machine I have now has a much larger ram than theirs. I am wondering if I do the test on this larger-ram machine and keep track of the memory usage, will the memory usage be the same on a smaller-ram machine or it will use even less memory?
Thanks!
Erben

You need to take a look at the JVM memory parameters. actually you can set the as much memory as you want to your JVM :
-Xmx2048m -> this param to set the max memory that the JVM can allocate
-Xms1024m -> the init memory that JVM will allocate on the start up
-XX:MaxPermSize=512M -> this for the max Permanent Generation memory
so in your case you can set the much memory as in the another machine. so you machine will not take more RAM than the Xmx value
and you may want to check this parameters also.
-XX:MaxNewSize= -> this need to be 40% from your Xmx value
-XX:NewSize=614m -> this need to be 40% from your Xmx value
also you may tell you JVM what type of GC to use like :
-XX:+UseConcMarkSweepGC
SO if you set this parameters in the both machines, you will get the same results and the same GC activity most likely.

Yes it will. This depends on the default maximum heap size. You can check your current maximum heap size using this command:
java -XshowSettings:vm
On my wife's laptop (Windows 8.1, 4 GB RAM, 32-Bit-Java-Runtime) it is 247.5 MB, while on my laptop (Windows 7, 8 GB RAM, 64-Bit-Java-Runtime) it is 903.12 MB.
This is determined by Java (see https://stackoverflow.com/a/4667635/3236102, though the values shown there are for server-class-machines, they might be different from normal machines).
If you want your vm to simulate a low-RAM-machine just use the -Xmx flag to limit your machine to less RAM (e.g. -Xmx128m for 128 MB RAM allocation).
The best thing might be to ask the users that encounter the Out Of Memory-issues to check their maximum heap size (using the command above) and set your machine to the same maximum heap size, so you have the same conditions as they have.

The issue can be reproduced with larger RAM.
First you need to get the heap size configuration from the people who reported the issue.
Use the same heap size to reproduce the issue.
Use below jvm params for heap settings.
-Xmx512m Max heap memory that is used to store objects
-XX:MaxPermSize=64m Max perm gen size. This space is used to store meta info like loaded classes etc

java heap size increasing and out of memory

I use java visual VM to monitor my heap and i see that the heap dump is showing bad signs
I think that this is why I am running out of memory,
How to limit the "size" (orange area) ?

Since your used heap size is stable, you can limit maximum heap size by using -Xmx512m to limit it to 512 MB for example.
This is a good article on what proper sizing should be (a bit out of date though):
http://publib.boulder.ibm.com/infocenter/javasdk/tools/index.jsp?topic=%2Fcom.ibm.java.doc.igaa%2F_1vg00014884d287-11c3fb28dae-7ff6_1001.html
Edit:
Since I see youre using NetBeans profiler, to set the option, just right click your project > Properties > Run > VM Options: -Xmx512m

how to increase java heap memory permanently?

I have one problem with java heap memory. I developed one client server application in java which is run as a windows service it requires more than 512MB of memory. I have 2GB of RAM but when I run my application it throws an exception
Out of memory error:java heap space
but I have already set heap size (maximum 512MB) in the java control panel and I still get the same error. I can't set heap size through the command line because my application runs as a windows service so how can I increase the default heap size?

The Java Virtual Machine takes two command line arguments which set the initial and maximum heap sizes: -Xms and -Xmx. You can add a system environment variable named _JAVA_OPTIONS, and set the heap size values there.
For example if you want a 512Mb initial and 1024Mb maximum heap size you could use:
under Windows:
SET _JAVA_OPTIONS = -Xms512m -Xmx1024m
under Linux:
export _JAVA_OPTIONS="-Xms512m -Xmx1024m"
It is possible to read the default JVM heap size programmatically by using totalMemory() method of Runtime class. Use following code to read JVM heap size.
public class GetHeapSize {
public static void main(String[]args){
//Get the jvm heap size.
long heapSize = Runtime.getRuntime().totalMemory();
//Print the jvm heap size.
System.out.println("Heap Size = " + heapSize);
}
}

This worked for me:
export _JAVA_OPTIONS="-Xmx1g"
It's important that you have no spaces because for me it did not work. I would suggest just copying and pasting. Then I ran:
java -XshowSettings:vm
and it will tell you:
Picked up _JAVA_OPTIONS: -Xmx1g

if you need to increase reserved memory, there are VM parameters -Xms and -Xmx, usage e.g. -Xms512m -Xmx512m . There is also parameter -XX:MaxPermSize=256m which changes memory reserved for permanent generationIf your application runs as windows service, in Control panels -> Administration tools -> Services you can add some run parameters to your service

You also use this below to expand the memory
export _JAVA_OPTIONS="-Xms512m -Xmx1024m -Xss512m -XX:MaxPermSize=1024m"
Xmx specifies the maximum memory allocation pool for a Java virtual machine (JVM)
Xms specifies the initial memory allocation pool.
Xss setting memory size of thread stack
XX:MaxPermSize: the maximum permanent generation size

Please note that increasing the Java heap size following an java.lang.OutOfMemoryError: Java heap space is quite often just a short term solution.
This means that even if you increase the default Java heap size from 512 MB to let's say 2048 MB, you may still get this error at some point if you are dealing with a memory leak. The main question to ask is why are you getting this OOM error at the first place? Is it really a Xmx value too low or just a symptom of another problem?
When developing a Java application, it is always crucial to understand its static and dynamic memory footprint requirement early on, this will help prevent complex OOM problems later on. Proper sizing of JVM Xms & Xmx settings can be achieved via proper application profiling and load testing.

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.