Minecraft

Where do I set RAM buffer, minimum RAM, Xms/Xmx, and what values?

Your server's memory settings live in the Startup tab, where you control the minimum RAM (Xms) and the RAM buffer that shapes the maximum (Xmx). Getting these right keeps the JVM stable and prevents the most common "instant crash."

The settings explained

In the Startup tab you'll find two RAM variables:

  • Xms (Minimum RAM): the memory floor. It must never exceed Xmx, or the server crashes instantly. Setting Xms equal to Xmx is a safe, common choice.
  • RAM Buffer (Xmx): the value you enter here lowers the JVM's usable Xmx by that much, reserving headroom to prevent OutOfMemory crashes.
  1. Set the RAM buffer based on your server size: 300–500MB for servers under 3GB, and 1000–3000MB for 3–10GB and larger.
  2. Set Xms at or below Xmx — many people set Xms equal to Xmx to avoid heap resizing.
  3. Save, then restart so the new values take effect.

Warning: Never set the minimum (Xms) above the maximum (Xmx) — that's the number-one cause of an instant crash on startup.

Frequently asked questions

Where exactly are these settings? In the Startup tab, exposed as the Minimum RAM and RAM Buffer variables.

Should Xms equal Xmx? That's a safe, common setup — it avoids the JVM resizing the heap. Just make sure Xms is never higher than Xmx.

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