This is the presentation I did at GIDS 2010.

1. Choosing a Concurrency Model Optimistic or Pessimistic with SQL Server Vinod Kumar M Technology Evangelist – Microsoft www.ExtremeExperts.com 20 / 04 / 10

12. SQL 2008 Isolation Levels Phenomena Allowed Isolation Levels Dirty Read Non-Repeatable Read Phantoms Update Conflict Concurrency Model READ UNCOMMITTED Yes Yes Yes No READ COMMITTED 1 Locking 2 Snapshot No No Yes Yes Yes Yes No No Pessimistic Optimistic REPEATABLE READ No No Yes No Pessimistic SNAPSHOT No No No Yes Optimistic SERIALIZABLE No No No No Pessimistic

13. Locking Decision Isolation level Scan type (Range, Table, Probe) # of rows in scan # of rows/page Locking strategy (Table, Page, Row) Operation type (scan, update) Current Activity Lock hints sp_IndexOption Settings

14. Walk through ISOLATION Levels