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I've looked at many different tutorials and Q&A websites, but I can't get it to work.

Right now Minecraft will only start if I have the -Xms1G JVM argument; if I try to increase it, I get the error:

Error occurred during initialization of VM Could not reserve enough space for 2097152KB object heap.

It sounds like either I don't have enough RAM available, or there's a program keeping Minecraft from taking up that much RAM. However, I have 8GB of RAM, so I have way more than enough.

Does anyone have any ideas on what's keeping me from increasing the amount?

  • I have had the same problem and I have 4 (3.9 Available) GB of RAM – Eisler 485 May 1 '15 at 0:28
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    Windows Mac Linux?? If its windows hit shift+control+escape and check to see what your Free RAM is.. Windows itself takes up quite a bit of RAM.. Just because your system has 8GB does not mean its actually all useable by a single application. – James May 1 '15 at 1:12
  • I have Windows, and more than enough RAM available. – Tandorvir May 3 '15 at 16:52
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    If you're using a 32 bit operating system you can't assign more than 1GB to java – imulsion May 3 '15 at 20:48
  • 2097152KB is ~2 TERABYTES. I don't think you have that much RAM. – SF. May 27 '19 at 9:59
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If you are going to use JVM arguments to define the memory allocation, be sure that you are not providing duplicate commands.

-Xms1G will set the MINIMUM HEAP to 1GB at start-up.

-Xmx1G will set the MAXIMUM HEAP to 1GB at start-up.

Generally, when I need more memory for Minecraft, I set the max heap and not the min heap.

For example;

java -Xmx2G -jar minecraft.jar

you could also set it like this:

java -Xms1G -Xmx2G -jar minecraft.jar

Avoid allocating too much RAM since that will starve the rest of the machine.

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  • Much more importantly, make sure that you actually set Xmx >= Xms! Not sure how Java would handle conflicting numbers, but better safe than unnecessarily rely on something some guy at Oracle (or Sun) put in the JVM code. – MrLemon May 1 '15 at 8:16
  • @ianc1215, I tried the first set of arguments you gave: "java.exe -Xmx2G -jar minecraft.jar" I got the error: "Error: Could not find or load main class java.exe" I really don't know what's wrong. Any ideas, anyone? – Tandorvir May 3 '15 at 16:47
  • minecraft. jar was just an example. you need to load the server jar file by its file name or put the arguments in the minecraft launcher for the client. – ianc1215 May 4 '15 at 0:01
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Okay, apparently I was using the 32-bit version of Java. I installed the 64-bit version and everything's working now. Thanks for your answers and comments, everybody!

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