An “In Memory” database refers to the data management system that stores data into the faster, computer memory (like RAM), in contrast to the usage of slower, disk storage. An “In Memory” database has the advantage of removing seek time from data queries, which vastly improves execution times. There are a couple of downsides for using In Memory. One is the added cost per unit of storage versus the relatively cheap disk storage. The other is the risk of losing all data in case of a power outage.
This topic is addressed on the following pages: