SQL Server 2014: What is Hekaton?

The Hekaton is a new database engine, also known as SQL Server In-Memory OLTP.
Hekaton collaborates with Microsoft Research and was released with Microsoft SQL Server 2014.

The Hekaton is a Greek word and meaning is 100 because this newly launched in-memory database is 100 times faster than the existing SQL Server engine.

If you don’t know about In-memory database, you can visit a below article.

Database Theory: What is In-memory Database?

If we look at traditional RDBMS system in which memory resources are very expensive and it optimize for disk storage.

The Hekaton allows us to work with memory-optimized tables and indexes which are entirely stored in main memory and still we can access via T-SQL like any other normal tables.

We can also create a stored procedure by adding the “WITH NATIVE_COMPILATION” clause that only reference to memory-optimized tables.

The Hekaton eliminates logical locks using automatic SNAPSHOT ISOLATION with multi-versioning, also have a lock free and latch free structures to access the data.

How Hekaton is different than SQL Server standard relational engine?

Very simple answer,

SQL Server standard relational engine developed basically for those data which resides on disk, and it reads and writes 8 KB per data pages to store them into the extents. This process requires lots of CPU I/O and memory.

With memory-optimized tables, there are no any data pages and extents. It stores only the data rows into memory with index pointer.

This engine also supports MVCC (Multiversion Concurrency Control) in which same data row has may be the different version at a single time so last updated version accessible by last most requests.

Because of MVCC nature, reader and writer process never block to eachother in Hekaton engine.

What is MVCC?
Anvesh Patel

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Thank anvesh, This is very useful.