Nov 2013 ~ How isolated are your sessions? ~ John Miner


Presenter: John Miner

Topic: How isolated are your sessions?
Downloads: Available on


Have you ever executed a TSQL program that crashed due to an integrity error?
Upon inspecting the job history, the error code states you have duplicate key values.
However; re-running the job does not reproduce the error. You probably had an transaction isolation level issue without knowing it.

I will be covering the following topics in this presentation:

  • Maintaining the ACID quality of transactions
  • How SQL Server implements transaction durability?
  • System versus User transactions
  • Transaction basics
  • Exploring the various transaction modes
  • Exclusive versus Shared locks
  • Blocking versus Deadlocks
  • How to detect them with my free code
  • How Isolation levels affect transaction behavior
  • What is a dirty read versus a phantom read?

At the end of the presentation, you will know how to fix the above scenario by changing the isolation level.


John has over twenty years of IT experience including a Masters degree in Computer Science from the University of Rhode Island with concentrations
in database technologies and programming languages. He also has Microsoft Certificates for Database Administration (MCDBA) and System Administration (MCSA).

John is currently a Senior SQL Server Developer / Administrator in charge of best practices by the IT team at Sensata Technologies. He is the PASS chapter
leader for Southern New England SQL Server Users Group.

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