Sql server® 2012 t-sql fundamentals

The 

SERIALIZABLE

 Isolation Level

Running under the REPEATABLE READ isolation level, readers keep shared locks until the end of the 

transaction. Therefore, you are guaranteed to get a repeatable read of the rows that you read the first 

time in the transaction. However, your transaction locks resources (for example, rows) that the query 

found the first time it ran, not rows that weren’t there when the query ran. Therefore, a second read 

in the same transaction might return new rows as well. Those new rows are called phantoms, and such 

reads are called phantom reads. This happens if, in between the reads, another transaction adds new 

rows that qualify for the reader’s query filter. 

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