Transaction (Process ID XX) was deadlocked on {some resource}.

Beatriece 20 Reputation points
2024-01-25T10:29:44.4633333+00:00

Hai all I'm running a query in my Azure SQL Database, I'm hit with an error: "Transaction (Process ID XX) was deadlocked on {some resource}." What's this deadlock , and how to fix it?

Azure SQL Database
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  1. Azar 29,520 Reputation points MVP Volunteer Moderator
    2024-01-25T10:39:38.53+00:00

    Hey Beatriece

    so a deadlock occurs when two or more transactions are in a standoff, each waiting for the other to release a resource.

    tre SQL Server identifies the deadlock and picks a "one" to break the tie. That one transaction gets rolled back, allowing the others to proceed. To prevent this deadlock duet, you can: Ensure your queries are as efficient as a well-tuned broomstick. to access resources in the same order to avoid clashes. Keep your transactions brief; long transactions increase the deadlock risk.

    If this helps kindly accept the answer thanks much.

    1 person found this answer helpful.

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  1. RahulRandive 10,486 Reputation points Volunteer Moderator
    2024-01-25T10:49:21.7533333+00:00

    Hi @Beatriece

    Deadlock occurs when two or more transactions are waiting for each other to release locks, resulting in a circular dependency. In your case, it seems that multiple processes are trying to update the same table simultaneously, causing a deadlock.

    To resolve this issue, you can try the following steps:

    1. Identify the queries that are causing the deadlock. You can use the SQL Server Profiler or Extended Events to capture the deadlock graph. The deadlock graph will provide you with information about the queries involved in the deadlock and the resources they are waiting for.

    Please find detailed blog on “How to obtain the deadlocks of your Azure SQL Database or Managed Instance? https://techcommunity.microsoft.com/t5/azure-database-support-blog/lesson-learned-19-how-to-obtain-the-deadlocks-of-your-azure-sql/ba-p/368847

    1. Once you have identified the queries causing the deadlock, you can optimize them to reduce the chances of a deadlock occurring. You can try to reduce the transaction size, use appropriate isolation levels, and avoid long-running transactions.
    2. Optimize your database indexes: Make sure that your database indexes are properly optimized and that you're not running any unnecessary queries. Improperly indexed tables can lead to more locks and deadlocks. 
    3. Reduce lock contention: If you are using a database that supports row-level locking, make sure you're using it. Use the smallest possible lock granularity to reduce lock contention. 
    4. Handle deadlocks properly: Your application should be able to handle deadlocks by detecting them and re-trying the transaction that caused the deadlock. Using a library like Dapper or Entity Framework will help you to handle deadlocks automatically for you. 
    5. Split the transactions: if your transactions are too big, you can consider splitting them into smaller transactions.
    6. Review the code: check the code in the parts where the error occurred, the problem may be a logic problem in your code that you need to fix.

    Please find detailed Microsoft documentation about “Analyze and prevent deadlocks in Azure SQL Database” below

    This article explain you how to identify deadlocks in Azure SQL Database, use deadlock graphs and Query Store to identify the queries in the deadlock, and plan and test changes to prevent deadlocks from reoccurring.

    https://learn.microsoft.com/en-us/azure/azure-sql/database/analyze-prevent-deadlocks?view=azuresql&tabs=ring-buffer 

    Also please find similar threads on deadlock and possible resolution below

    https://learn.microsoft.com/en-us/answers/questions/1158263/transaction-(process-id-137)-was-deadlocked-on-loc

    I hope this helps. Thank you!

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