How to Determine the Current Transaction Isolation Level in SQL Server?

Determining Your SQL Server Transaction Isolation Level: A Quick Guide

Knowing your current transaction isolation level is vital for understanding database behavior and performance. SQL Server offers various isolation levels, each balancing data protection and speed.

Retrieving Your Transaction Isolation Level

Use this simple query to identify your current transaction isolation level:

SELECT CASE transaction_isolation_level
    WHEN 0 THEN 'Unspecified'
    WHEN 1 THEN 'ReadUncommitted'
    WHEN 2 THEN 'ReadCommitted'
    WHEN 3 THEN 'Repeatable'
    WHEN 4 THEN 'Serializable'
    WHEN 5 THEN 'Snapshot'
END AS TRANSACTION_ISOLATION_LEVEL
FROM sys.dm_exec_sessions
WHERE session_id = @@SPID;

This query will return one of the following:

• Unspecified
• ReadUncommitted
• ReadCommitted
• Repeatable
• Serializable
• Snapshot

Understanding Isolation Level Constants

For a complete list of isolation level constants, refer to Microsoft's documentation:

https://www.php.cn/link/10ada88209bc465aa0ebd61bc248733e

The Importance of Transaction Isolation Levels

The transaction isolation level dictates the degree of data protection during concurrent access. Higher levels offer greater protection but can reduce performance due to increased locking. Choosing the right level is key to balancing database performance and data integrity.

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