Are you ready to learn how to avoid deadlocks in SQL Server Stored Procedures? Our SQL Server Support team is here to lend a hand with your queries and issues.

About Deadlocks in SQL Server Stored Procedures

A deadlock is a result of two or more operations attempting to access resources that are locked by each other. This affects the database resources negatively as the processes are stuck waiting endlessly for the other one to finish. In this scenario, the SQL Server will terminate the contention issue.

In other words, it picks one of the processes stuck in the deadlock and forces it to rollback its actions.

Since each deadlock is unique, each solution requires a different approach depending on the situation’s characteristics.

Let’s take a quick look at the different types of deadlocks in SQL Server:

1. Bookmark lookup deadlock

   This type of deadlock occurs because of a conflict between the DML statements and the select statement.
2. Range scan deadlock

   The Range scan deadlock result while using the SERIALIZABLE isolation level at the session or server level.
3. Cascading constraint deadlock

   This type of deadlock occurs when we delete or update a record from the parent table. It results in locks on the child table in order to prevent orphan records. Hence, we have to modify data in the child table first.
4. Intra-query parallelism deadlock

   If the SQL Server is executing a query in parallel mode, it results In multiple threads. These threads may start blocking one another in some scenarios. That is how we wind up with an Intra-query parallelism deadlock.
5. Reverse object order deadlock

   When multiple transactions access objects in a different order, it results in blocking resources for each session, ending up in a Reverse object order deadlock.

How to avoid & reduce Deadlock in SQL Server Stored Procedure

Our experts have put together this list of tips to help you avoid a deadlock in SQL Server:

• Make sure the transactions are short. This prevents holding locks in a transaction for a long duration.
• Our experts recommend changing the isolation level to SNAPSHOT ISOLATION or READ COMMITTED SNAPSHOT ISOLATION. This will change the SQL Server locking mechanism.
• Try to access objects by following a logical manner for multiple transactions.
• Indexes that the foreign key columns can eliminate deadlocks because of cascading referential integrity.
• A covering index helps the chances of a deadlock.
• Try to set deadlock priorities with the SET DEADLOCK_PRIORITY session variable.
• Use the error handling option with try-catch blocks in order to trap the deadlock error.

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Conclusion

To wrap up, our Support Engineers introduced us to different types of deadlocks. We also got a look at different ways to avoid deadlocks in SQL Server stored procedures.