Swap is a part of the disk the system uses as reserve memory when RAM fills up. Without it, if you run out of memory, Linux kills the biggest process, which is usually exactly your game server or your database.
Do you already have it?
swapon --show
free -hIf swapon --show prints nothing, you have no swap.
Create a 2 GB swap file
fallocate -l 2G /swapfile
chmod 600 /swapfile
mkswap /swapfile
swapon /swapfile
echo '/swapfile none swap sw 0 0' >> /etc/fstabThe last line keeps it active after a reboot. 1-2 GB is usually enough; it takes that much disk space.
Only use it when really needed
By default Linux starts moving things to swap fairly early. On a server it is better to wait until it is needed:
sysctl vm.swappiness=10
echo 'vm.swappiness=10' > /etc/sysctl.d/99-swappiness.confWhat swap does not do
Disk is far slower than RAM. If your game server lives in swap, it will stutter anyway. Use it as a safety net for occasional peaks; if free -h shows it in constant use, what you need is more RAM: upgrade the plan, with no migration needed.