What Happens to Pending Database Transactions When a Connection Closes?

Transaction Fate upon Connection Closure

When a database connection is closed, what becomes of pending transactions is a matter of debate. Are they immediately forfeited, delayed in their resolution, or indefinitely suspended?

Transaction Behavior in Various Scenarios

• Immediate Rollback: Uncommitted transactions are promptly discarded upon connection closure.
• Delayed Rollback: Transactions linger in an uncommitted state for a set duration before being rolled back.
• Unresolved State: Transactions remain in an unresolved state, potentially leading to errors when the connection is reused.

Impact of Connection Pooling

The behavior may change with connection pooling. When connections are released back into the pool, uncommitted transactions may remain active until the connection is assigned to a new client.

Recommended Solutions

To ensure consistent transaction handling, consider employing the following strategies:

• Implement client-side checks to identify and manually roll back unfinished transactions, e.g., "IF @@TRANCOUNT <> 0 ROLLBACK TRAN".
• Utilize the "SET XACT_ABORT ON" command to automatically clean up open transactions.
• Prioritize the use of the "SET XACT_ABORT ON" setting to guarantee transaction resolution.

Pooling Considerations

As noted in the SQL Team blog, connection pooling can allow uncommitted transactions to persist. This has implications for locks and timeouts, potentially causing unnecessary delays.

According to MSDN, distributed transactions remain pending even after connection closure. This flexibility enables delayed resolution of such transactions, but it also emphasizes the need for careful transaction management to avoid potential errors.

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