Over a million developers have joined DZone.

Visualizing SQL Server Transaction Isolations

· Database Zone

Build fast, scale big with MongoDB Atlas, a hosted service for the leading NoSQL database. Try it now! Brought to you in partnership with MongoDB.

Michael J. Swart - Visualizing Transaction Isolations For SQL Server

The four standard SQL Server isolation levels that SQL Server provides are READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ and SERIALIZABLE. (I leave aside the row-versioning levels for another day). SQL Server implements these isolation levels using locks.

In fact I was listening to Kimberly Tripp’s MCM Preparation Video “Snapshot Isolation“. She gives a recap of isolation levels and describes the locks taken during an index scan using READ COMMITTED. She says:

“(For readers) READ COMMITTED uses shared locks … the shared locks are only held for the life of the resource being read. You can almost think of shared locks kind of trickling through the table but not being kept.”

She invites us to visualize this scenario and so I did, literally. Enjoy!



I thought this a cute, yet useful, visualization. That and it's good to see animated Gif's put to actually good use.

Now it's easier than ever to get started with MongoDB, the database that allows startups and enterprises alike to rapidly build planet-scale apps. Introducing MongoDB Atlas, the official hosted service for the database on AWS. Try it now! Brought to you in partnership with MongoDB.


The best of DZone straight to your inbox.

Please provide a valid email address.

Thanks for subscribing!

Awesome! Check your inbox to verify your email so you can start receiving the latest in tech news and resources.

{{ parent.title || parent.header.title}}

{{ parent.tldr }}

{{ parent.urlSource.name }}