Why Does TransactionScope Escalate to MSDTC on Some Machines but Not Others?

TransactionScope and MSDTC: Inconsistent Behavior Across Machines

Issue:

A .NET application utilizing TransactionScope exhibits inconsistent behavior regarding MSDTC escalation. On some developer machines, the transaction automatically escalates to Microsoft Distributed Transaction Coordinator (MSDTC), requiring MSDTC to be enabled. On others, the same code functions correctly without MSDTC.

Context:

• TransactionScope manages data access within a transaction.
• MSDTC activation is necessary on certain machines to prevent errors.
• The problem arises when using two database connections within a single TransactionScope. The second connection attempt triggers MSDTC escalation on affected systems.

Investigation:

Initial assumptions about SQL Server version discrepancies (2005 vs. 2008) proved incorrect. The root cause lies in SQL Server 2005's limitations: it doesn't support multiple connections within a single TransactionScope, regardless of their opening sequence. Attempting a second connection forces escalation. SQL Server 2008, conversely, permits multiple connections within a TransactionScope, provided they aren't simultaneously open. Premature connection closing and reopening, potentially through connection pooling and data access layers (like SqlTableAdapter), can also trigger escalation in SQL Server 2005.

Resolution:

For SQL Server 2005, maintaining a single, globally-scoped, open connection throughout the transaction prevents MSDTC escalation. However, this deviates from best practices advocating efficient connection management (opening and closing as needed). Upgrading to SQL Server 2008 or later is the recommended solution to avoid this limitation and maintain best practices.

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