It is contrasted with database management systems that employ a disk storage mechanism.
Specifically in the event of a power loss, intentional or otherwise, data stored in volatile RAM is lost.
[6] With the introduction of non-volatile random-access memory technology, in-memory databases will be able to run at full speed and maintain data in the event of power failure.
Volatile memory-based IMDBs can, and often do, support the other three ACID properties of atomicity, consistency and isolation.
Hot data should be stored in ways offering fast retrieval and modification, often accomplished by in-memory storage but not always.
A database in this form of memory combines very fast access speed with persistence over reboots and power losses.