An isolation level determines the degree of isolation of 
data between concurrent transactions. The default SQL 
Server isolation level is Read Committed. 

Here are the other isolation levels (in the ascending order 
of isolation): Read Uncommitted, Read Committed, Repeatable 
Read, Serializable

there are 5types of isolation level
1.ecoas
2.read commited
3.read uncommited
4.repetable read
5.synchronized

Isolaton is the reduce the concurrency
Default 1)Read Commit
2)Read Uncommit
3)Repatable read
4) Serizable--