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Welcome to Kodlogs, programming questions and answer website.

In this article, we are going to learn the reason of “Could not reserve enough space for object heap” error while performing some specific tasks. This error mostly occurs when the Java process cannot create virtual machine due to some memory constraints that encounter on the running system.


Generally, there are two possible situations when the user can encounter this error;

  • First, when the user launches a java process with a max heap size limit parameter and value is more than what the process can have during the operating system. The heap differs based on several constraints;
  1. Hardware architecture 32/64 bits.
  2. JVM bit version 32/64 bit
  3. The operating system we mostly used.
  • Secondly, when the java process is unable to reserve some specified amount of memory due to some other applications that are running on the same system and consume memory.


We can control the heap size limit of JVM by using two methods;

  • First, use java command line parameters at each JVM initialization.
  • Second use environment variable JAVA_OPTS to configure the java command line parameters globally. Due to this reason, each JVM initialization on the system will automatically use the configuration set in the environment variable.
JAVA_OPTS=”Xms256m – Xms512m”


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