The main-memory engine that handles the in-memory tables (M-tables) and the disk-based engine that handles the storage of disk-based tables (D-tables) use different data storage architectures.

In-memory engine is designed for maximum performance. Knowing that data is always stored in main-memory allows for use of data structures and data access methods that are designed to minimize the computational (CPU) cost of retrieving or updating database records.

Disk-based engine, however, can reduce disk access. Reduced disk access is achieved by data structures and access methods that trade disk access for additional computational processing. Therefore, an in-memory engine has the potential to outperform a disk-based engine even when the latter has cached all the data in the memory buffer pools because it consumes fewer processor cycles to access database records.