You can use Paging to add a supplement virtual memory on your server. This supplement memory doesn't reside on the physical memory assigned to the machine, it's a space made on a hard disk and saved for using as extra memory by your machine or server.
You can add this extra memory to your instance using the following commands:
sudo /bin/dd if=/dev/zero of=/var/swap.1 bs=1M count=1024
sudo /sbin/mkswap /var/swap.1
sudo chmod 600 /var/swap.1
sudo /sbin/swapon /var/swap.1