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Could not reserve enough space for object heap

20 Nov 2020 6:19 pm || 0

Newbie and experienced programmers have faced this error at some point of their lives – Could not reserve enough space for object heap. This is irritating when you have some real work to be done! The error is raised when the Java process is not able to create a virtual machine due to lack of memory space.

Modifying the memory size required for running JVM might solve the problem. In this post, we will take a closer look at the error and also its solutions.

What is the “Could not reserve enough space for object heap” error?

Heap size is the memory space provided for storing Java objects. This heap size depends upon certain factors that include JVM bit version, system hardware and operating system. The Xmx and Xms VM arguments can be used to allocate maximum and minimum heap size.

The 3 main causes of this error are –

  • The Java application was executed without properly specifying the heap size needed
  • The specified heap size is more than the physical memory of your system
  • The mentioned maximum heap size is larger than the heap size of the JVM

How to Fix the Heap Size Error?

The ways to get rid of this error for good are –

  1. Mention heap size beforehand  

You can do this with the command java -Xmx512M AppName. Usually, this error occurs in 32 bit JVM as it requires contiguous free space in the memory to run applications. Also, using 64 bit JVM instead of 32 bit is a better option.

  1. Specify a heap size lower than your system memory

Suppose you have 2 GB of RAM. Then specify a heap size lower than that using the command below:

java -Xms1336M -Xmx1336M AppName

Another way to tackle theCould not reserve enough space for object heap error, in this case, is by mentioning the heap size in the Java Options environment variable. For this, go to Control Panel>System>Advanced>Environment Variables>System Variables. Then create a new variable name _JAVA_OPTIONS with heap size -Xmx256M.

  1. Mention heap size lower than the JVM size      

In order to have enough free space to run your application smoothly, specify a lower heap size using this command –

java -Xms1336M -Xmx1336M AppName

Make sure to check already assigned memory and heap sizes, before modifying them. It is best to use the 64-bit version of Java to avoid the

Could not reserve enough space for object heap error.