How to configure NuoDB to benefit from System Memory
Database performance is limited by the speed that it takes to read data from the physical media it's stored on. This limitation can be reduced by caching frequently referenced database atoms in memory, as memory access is far faster than network communication with other nodes or reading from non-volatile storage media.
Benefitting from Memory
Increasing the available memory allows more atoms to be cached in memory, which reduces the number of network requests and I/O operations that need to be performed. The amount of memory a NuoDB process is allowed to use is controlled by the --mem database option. By default this is 2 GB, which is typically much less than the available memory on a production system.
Memory should be set to the highest value such that swapping doesn't occur. Swapping is when the OS runs out of available hardware memory and is forced to write some to disk, which negates any performance benefit from caching. --mem is a soft limit and a NuoDB process may use about 30% more, so this overhead should be accounted for when determining the value.