The SQL Server 2014 in-memory online transaction processing (OLTP) engine, previously code-named Hekaton, allows you to create in-memory, optimized OLTP tables within a conventional relational database. It is one of the key, new, performance-related architectural enhancements to SQL Server Database Engine. Like traditional transactions on disk-based tables, the transactions on in-memory-optimized OLTP tables are fully atomic, consistent, isolated, and durable. The in-memory OLTP engine solves problems in high-concurrency situations as it uses data structures that are entirely latch-free (lock-free), which means there are no latches or spinlocks on performance-critical paths in the system. Instead, it uses an optimistic Multiversion Concurrency Control (MVCC) technique that provides transaction isolation semantics, which help avoid interference among transactions. Thus, any user process can access any row in a table without acquiring latches or locks...