Snapshot Table Hint in SQL Server

 

This hint specifies that data read by any statement in a transaction will be the transactionally consistent version of the data that existed at the start of the transaction.

Consider a situation where a reporting system needs to generate reports based on data that remains consistent throughout the report generation process, regardless of concurrent transactions modifying the data. To achieve this, the SNAPSHOT isolation level is employed:

BEGIN TRANSACTION; -- Set the transaction isolation level to SNAPSHOT using a hint SELECT * FROM TableName WITH (SNAPSHOT) WHERE Condition = @Condition; -- Perform additional queries or operations within the transaction COMMIT TRANSACTION;

 

By setting the transaction isolation level to SNAPSHOT, the database engine generates a consistent snapshot of the database at the start of the transaction. This snapshot ensures that the data remains consistent and does not change during the transaction, even if other transactions modify the data concurrently. This allows the reporting system to generate reports based on a stable and consistent view of the data, improving data integrity and accuracy. However, it’s essential to consider the overhead associated with maintaining snapshot versions of data, especially in high-concurrency environments.

Note : The hint 'SNAPSHOT' is valid only with memory optimized tables