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‎azure-sql/database/analyze-prevent-deadlocks.md‎

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---
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title: Analyze and Prevent Deadlocks
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titleSuffix: Azure SQL Database
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description: Learn how to analyze deadlocks and prevent them from reoccurring in Azure SQL Database and Fabric SQL database.
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description: Learn how to analyze deadlocks and prevent them from reoccurring in Azure SQL Database and SQL database in Fabric.
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author: rwestMSFT
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ms.author: randolphwest
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ms.reviewer: mathoma, dfurman, wiassaf
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ms.date: 09/23/2025
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ms.date: 10/09/2025
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ms.service: azure-sql-database
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ms.subservice: performance
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ms.topic: troubleshooting-general
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monikerRange: "=azuresql || =azuresql-db || =fabricsql"
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ms.custom:
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- ignite-2024
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- sfi-image-nochange
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monikerRange: "=azuresql || =azuresql-db || =fabricsql"
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---
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# Analyze and prevent deadlocks in Azure SQL Database and Fabric SQL database
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# Analyze and prevent deadlocks in Azure SQL Database and SQL database in Fabric
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[!INCLUDE [appliesto-sqldb-fabricsqldb](../includes/appliesto-sqldb-fabricsqldb.md)]
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In this article, we use the `AdventureWorksLT` sample database to set up alerts for deadlocks, cause an example deadlock, analyze the deadlock graph for the example deadlock, and test changes to prevent the deadlock from reoccurring.
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We use the [SQL Server Management Studio](/sql/ssms/download-sql-server-management-studio-ssms) (SSMS) client in this article, as it contains functionality to display deadlock graphs in an interactive visual mode. You can use other clients such as [Azure Data Studio](/azure-data-studio/download-azure-data-studio), the [MSSQL extension for Visual Studio Code](/sql/tools/visual-studio-code-extensions/mssql/mssql-extension-visual-studio-code), [sqlcmd](/sql/tools/sqlcmd/sqlcmd-utility), or your favorite T-SQL querying tool to follow along with the examples, but you might only be able to view deadlock graphs as XML.
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We use the [SQL Server Management Studio](/ssms/install/install) (SSMS) client in this article, as it contains functionality to display deadlock graphs in an interactive visual mode. You can use other clients such as the [MSSQL extension for Visual Studio Code](/sql/tools/visual-studio-code-extensions/mssql/mssql-extension-visual-studio-code), [sqlcmd](/sql/tools/sqlcmd/sqlcmd-utility), or your favorite Transact-SQL querying tool to follow along with the examples, but you might only be able to view deadlock graphs as XML.
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### Create the AdventureWorksLT database
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To follow along with the examples, create a new database in Azure SQL Database and select **Sample** data as the **Data source**.
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For detailed instructions on how to create `AdventureWorksLT` with the Azure portal, Azure CLI, or PowerShell, select the approach of your choice in [Quickstart: Create an Azure SQL Database single database](single-database-create-quickstart.md).
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For detailed instructions on how to create `AdventureWorksLT` with the Azure portal, Azure CLI, or PowerShell, select the approach of your choice in [Quickstart: Create a single database in Azure SQL Database](single-database-create-quickstart.md).
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### Set up deadlock alerts in the Azure portal
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To set up alerts for deadlock events, follow the steps in the article [Create alerts for Azure SQL Database using the Azure portal](alerts-create.md).
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To set up alerts for deadlock events, follow the steps in the article [Create alerts for Azure SQL Database and Azure Synapse Analytics using the Azure portal](alerts-create.md).
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Select **Deadlocks** as the signal name for the alert. Configure the **Action group** to notify you using the method of your choice, such as the **Email/SMS/Push/Voice** action type.
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To configure an Azure Storage container, first create or select an existing Azure Storage account, then create the container. Generate a Shared Access Signature (SAS) token for the container. This section describes completing this process in the Azure portal.
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> [!NOTE]
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> If you wish to create and configure the Azure Storage blob container with PowerShell, see [Event File target code for extended events in Azure SQL Database and SQL database in Fabric](xevent-code-event-file.md). Alternately, you might find it convenient to [Use Azure Storage Explorer](#use-azure-storage-explorer) to create and configure the Azure Storage blob container instead of using the Azure portal.
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> If you wish to create and configure the Azure Storage blob container with PowerShell, see [Create an event session with an event_file target in Azure Storage](xevent-code-event-file.md). Alternately, you might find it convenient to [Use Azure Storage Explorer](#use-azure-storage-explorer) to create and configure the Azure Storage blob container instead of using the Azure portal.
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#### Create or select an Azure Storage account
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1. Select **+ Container** to create a new container. The New container pane appears.
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1. Enter a name for the container under **Name**.
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1. Select **Create**.
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1. Select the container from the list after it is created.
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1. Select the container from the list after it's created.
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#### Create a shared access token
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## Cause a deadlock in AdventureWorksLT
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> [!NOTE]
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> This example works in the `AdventureWorksLT` database with the default schema and data when RCSI is enabled. See [Create the AdventureWorksLT database](#create-the-adventureworkslt-database) for instructions to create the database.
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To cause a deadlock, you need to connect two sessions to the `AdventureWorksLT` database. We refer to these sessions as **Session A** and **Session B**.
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In **Session A**, run the following Transact-SQL. This code begins an [explicit transaction](/sql/relational-databases/sql-server-transaction-locking-and-row-versioning-guide#starting-transactions) and runs a single statement that updates the `SalesLT.Product` table. To do this, the transaction acquires an [update (U) lock](/sql/relational-databases/sql-server-transaction-locking-and-row-versioning-guide#behavior-when-modifying-data) on one row on table `SalesLT.Product` which is converted to an exclusive (X) lock. We leave the transaction open.
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```sql
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BEGIN TRANSACTION;
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UPDATE SalesLT.Product
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SET SellEndDate = SellEndDate + 1
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WHERE Color = 'Red';
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```
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Now, in **Session B**, run the following Transact-SQL. This code doesn't explicitly begin a transaction. Instead, it operates in [autocommit transaction mode](/sql/relational-databases/sql-server-transaction-locking-and-row-versioning-guide#starting-transactions). This statement updates the `SalesLT.ProductDescription` table. The update takes out an update (U) lock on 72 rows on the `SalesLT.ProductDescription` table. The query joins to other tables, including the `SalesLT.Product` table.
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```sql
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UPDATE SalesLT.ProductDescription
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SET Description = Description
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FROM SalesLT.ProductDescription AS pd
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INNER JOIN SalesLT.ProductModelProductDescription AS pmpd
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ON pd.ProductDescriptionID = pmpd.ProductDescriptionID
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INNER JOIN SalesLT.ProductModel AS pm
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ON pmpd.ProductModelID = pm.ProductModelID
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INNER JOIN SalesLT.Product AS p
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ON pm.ProductModelID = p.ProductModelID
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WHERE p.Color = 'Silver';
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```
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To complete this update, **Session B** needs a shared (S) lock on rows on the table `SalesLT.Product`, including the row that is locked by **Session A**. **Session B** is blocked on `SalesLT.Product`.
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Return to **Session A**. Run the following Transact-SQL statement. This runs a second `UPDATE` statement as part of the open transaction.
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```sql
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UPDATE SalesLT.ProductDescription
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SET Description = Description
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FROM SalesLT.ProductDescription AS pd
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INNER JOIN SalesLT.ProductModelProductDescription AS pmpd
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ON pd.ProductDescriptionID = pmpd.ProductDescriptionID
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INNER JOIN SalesLT.ProductModel AS pm
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ON pmpd.ProductModelID = pm.ProductModelID
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INNER JOIN SalesLT.Product AS p
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ON pm.ProductModelID = p.ProductModelID
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WHERE p.Color = 'Red';
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```
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The second update statement in **Session A** is blocked by **Session B** on the `SalesLT.ProductDescription`.
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**Session A** and **Session B** are now mutually blocking one another. Neither transaction can proceed, as they each need a resource that is locked by the other.
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After a few seconds, the deadlock monitor identifies that the transactions in **Session A** and **Session B** are mutually blocking one another, and that neither can make progress. You should see a deadlock occur, with **Session A** chosen as the deadlock victim. An error message appears in **Session A** with text similar to the following:
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```output
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Msg 1205, Level 13, State 51, Line 7
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Transaction (Process ID 91) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction.
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```
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**Session B** completes successfully.
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## Cause a deadlock
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If you [set up deadlock alerts in the Azure portal](#set-up-deadlock-alerts-in-the-azure-portal), you should receive a notification shortly after the deadlock occurs.
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Because [optimized locking](/sql/relational-databases/performance/optimized-locking) is always enabled in Azure SQL Database and SQL database in Fabric, deadlocks are less likely. For more information, and for an example of a deadlock that can occur with optimized locking, see [Optimized locking and deadlocks](/sql/relational-databases/sql-server-deadlocks-guide#optimized-locking-and-deadlocks).
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## View deadlock graphs from an XEvents session
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