Forrester defines an in-memory database platform as:
A database technology that stores all or partial data in memory on either a single or distributed server to support transactional, operational, and/or analytical workloads.
The in-memory database platform represents a new space within the broader data management market. Enterprise architecture (EA) professionals invest in in-memory database platforms to support real-time analytics and extreme transactions in the face of unpredictable mobile, Internet of Things (IoT), and web workloads.
SAP, Oracle, IBM, Teradata and Microsoft are the leaders in ‘The Forrester Wave™: In-Memory Database Platforms, Q3 2015’
Source: Forrester Research