Minecraft servers live and die by garbage-collection pauses: every time Java stops the world to clean memory, your tick rate hiccups. Aikar's flags configure the G1 collector to clean smaller amounts more often, pre-touch the whole heap at startup and avoid explicit GC calls from plugins - the standard set documented by PaperMC, with the large-heap variant (12 GB and up) adjusting five G1 sizing values exactly as Aikar's original research specifies. The generator switches variants automatically based on your RAM input.
Save the file next to your server jar, make it executable on Linux (chmod +x start.sh) and run it from a terminal or screen/tmux session. The auto-restart loop brings the server back after crashes and /stop - handy for unattended machines. On a GGameHost server you never touch any of this: tuned startup flags are applied for you and RAM changes are a plan setting, not a script edit.
A community-standard set of JVM arguments that tune Java's G1 garbage collector for Minecraft servers. They smooth out memory cleanup so the server spends less time paused - the difference shows most on modded and busy servers. The exact set (and the large-heap variant) comes from Aikar's original research, as documented by the PaperMC project.
So the Java heap never has to grow mid-game. Growing the heap causes pauses at the worst possible time; pre-allocating the full amount (with -Xms equal to -Xmx) plus the AlwaysPreTouch flag avoids that entirely on a dedicated server.
Not all of the machine. Leave 1-2 GB for the operating system and Java's own overhead - on an 8 GB server, -Xmx6G is a sensible ceiling. Our RAM calculator sizes the total machine; this page turns that number into the start command.
They fix garbage-collection stutter specifically. If your tick rate is low because of too many entities, chunk generation or a heavy plugin, flags will not save you - CPU single-thread speed and pruning the workload will.