13. Understanding the Locking System : User-Controlled Locking--SET LOCKMODE : Isolation Levels : Inconsistencies and Isolation Levels
 
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Inconsistencies and Isolation Levels
The following table shows how the ANSI standard defines which inconsistencies are possible (Yes) and impossible (No) for a given isolation level:
Isolation Level
Dirty Read
Non-Repeatable Read
Phantom Rows
Read Uncommitted
Yes
Yes
Yes
Read Committed
No
Yes
Yes
Repeatable Read
No
No
Yes
Serializable
No
No
No
For programmers who are aware of possible inconsistencies, lower degrees of isolation can improve throughput.