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Deploying Crystal Reports
Introduction : Configuring the ODBC driver : Understanding transactions and isolation levels
 

Understanding transactions and isolation levels

SQL defines isolation levels in terms of the inconsistencies they allow:
The following table identifies which inconsistencies are either permitted or prevented by each isolation level.
Table 1. Transaction isolation levels
Isolation
Dirty read
Nonrepeatable read
Phantom read
READ UNCOMMITTED
Permitted
Permitted
Permitted
READ COMMITTED
Prevented
Permitted
Permitted
REPEATABLE READ
Prevented
Prevented
Permitted
SERIALIZABLE
Prevented
Prevented
Prevented
* Dirty read
* Nonrepeatable read
* Phantom read