In-Memory OLTP introduces a new type of index for memory-optimized tables in SQL Server 2014: the hash index. This new index type is optimized for index seek operations, i.e. finding the rows corresponding to a given set of equality predicates; for example, ‘o_id=8 AND od_id=4’.
We believe that the In-Memory OLTP engine advances the industry state of the art with respect to concurrency control. The main reason for this advancement is due to the combination of lock free algorithms and the row-versioned architecture of the engine.
The new In-Memory OLTP feature introduces memory-optimized tables and natively compiled stored procedures in SQL Server 2014, to optimize performance and scalability of OLTP workloads. To benefit from this technology in an existing SQL Server application, you need to migrate the performance critical tables and stored procedures to memory-optimized tables and natively compiled stored procedures respectively.