Difference between Transaction Isolation Level 1 & 2
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Posted By:   Manish_Vyas
Posted On:   Friday, October 29, 2004 06:20 AM

I am a bit confuse between Transaction Isolation Level 1& 2. Will someone throw light on this with example.

Re: Difference between Transaction Isolation Level 1 & 2

Posted By:   neeraj_pandey  
Posted On:   Friday, January 21, 2005 10:42 AM

Can you please explictly state the confusion. I am writing the defination of each of the isolation level.

* TRANSACTION_READ_UNCOMMITTED: The transaction can read uncommitted data, i.e., data being changed by another transaction concurrently.

* TRANSACTION_READ_COMMITTED: This level results in the prevention of a transaction from reading uncommitted changes in other concurrent transactions. This level ensures that dirty reads are not possible.

* TRANSACTION_REPEATABLE_READ: In addition to the prevention associated with TRANSACTION_READ_COMMITTED, this level ensures that reading the same data multiple times will receive the same value even if another transaction modifies the data. Methods with this isolation level, besides having the same behavior as TRANSACTION_READ_COMMITTED, can only execute repeatable reads.

* TRANSACTION_SERIALIZABLE: The transaction has exclusive read and update privileges to data by locking it; other transactions can neither write nor read the same data. It is the most restrictive transaction isolation level and it ensures that if a query retrieves a result set based on a predicate condition and another transaction inserts data that satisfy the predicate condition, re-execution of the query will return the same result set.

Hope it helps
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