How Can I Add Swap on CentOS 7

To increase your server’s responsiveness, the very simple way is to add some swap space; it will guard your server against out-of-memory errors that will arise in your application. Swap is an area located in your storage drive where your operating system can temporarily store data that it can no longer hold in memory.

For example, if you don’t have swap, and your server is running out of memory, in that case the server will start to kill applications to free up some space, or even, crash can occur. That will result in server downtime; also you will lose unsaved data. For reliable data accessing, some applications may require swap to function.