![]() ![]() You may prevent deadlock by using UPDLOCK, ROWLOCK, NOLOCK table hints. In case your database is facing frequent Deadlock situations then it will impact the application performance. In MS-SQL Server, a Deadlock is a situation where 2 or more transactions are trying to access the same resource but they keep waiting for each other to complete the action. It gives you an interface where each and every event in MS-SQL is captured, based on that developers and DBA can identify the problems and give their resolution. This tool helps developers with tracing, debugging and troubleshooting in MS-SQL Server. SQL Server Profiler is a tool given by Microsoft which is available with SQL Server instance. In the above output window, move your cursor over Oval shapes and it will show you the statement which is causing the Deadlock situation. Now, execute the queries as mentioned above.Īs soon as the Deadlock will occur you may notice Deadlock in event class.Ĭlick on the Deadlock graph and it will present a diagram presenting a Deadlock situation. Refer to the below screenshot with the highlighted area. Click on the Events Selection tab.Ĭheck Show all events, expand the Locks section to select Deadlock graph, Lock: Deadlock and Lock: Deadlock Chain. To open this, go to Tools -> SQL Server Profiler So, the next task is to trace the Deadlock and resolve this.įollow the below steps to trace and detect Deadlock.Ĭopy below queries in 3 different Query windows and execute in the order it is mentioned.īefore executing the above query, first, open SQL Server Profile. Once you know that frequent Deadlock occurs in your application database and in result the application performance gets hampered. How to trace and detect a Deadlock in SQL Server? Syntax – select * from Products with(NOLOCK) where Id = 1 It stops read and write transactions from blocking the same resource. NOLOCK is used to read data from the SQL Server table by ignoring any locks imposed on it. Syntax – select * from Products with(ROWLOCK) where Id = 1 The UPDLOCK is used to apply a lock on a resource that possibly can be updatedĪ select statement before updating the record in the same transaction, this will help to prevent a Deadlock situation. The below table tells about UPDLOCK, ROWLOCK and NOLOCK uses in SQL Server. Now, run both queries and you will not see any Deadlock error. ![]() We will not make any changes in the second query window. UPDATE #Table2 SET City= 'Chennai' WHERE Id = 1 UPDATE #Table1 SET Name = 'Shyam' WHERE Id = 1 SELECT Id FROM #Table2 WITH (UPDLOCK) WHERE Id=1 - This line Added So, the first query window script will look like this – BEGIN TRANSACTION SELECT Id FROM #Table2 WITH (UPDLOCK) WHERE Id=1 ![]() In order to resolve this, add the below line in the first query window. Also, try to impose a lock for a short span of time. If we talk about the above script, simply we can use UPDLOCK to avoid SQL Server Deadlock. The very first thing is to optimize your stored procedures and make sure to use small transaction blocks.Īnother way is to use a lock hint within your query. ![]() There are multiple ways to avoid the Deadlock situations in SQL Server. Exclusive Lock – In case a resource is an exclusive lock, then it can be read as well as written.Shared Lock is used to preventing data from being updated. Shared Lock – It is used for reading data so it is also called a read lock.To achieve this lock operation is used to isolate the transactions. Shared vs Exclusive LockĪ well-optimized SQL Query is written in a manner where one transaction is trying to read the data from a table and no other transactions can update the same data at the same time. Later, in this article, we will explore How to trace and detect a Deadlock in SQL Server Profile and then we will see the way we can minimize or prevent the Deadlock situation. In the above scenario, the first query window will run successfully, however, the 2nd query window will be in a Deadlock situation and you will get the below output – If you want to increase it, you can set it to10 or 15 seconds delay. Make sure to execute the second query window immediately after executing the first one as the WAITFOR DELAY is 5 seconds. Next, open another query window and execute the below script. Run below query in new query window – BEGIN TRANSACTION In this case, the Deadlock scenario may occur.īelow SQL Query will help us to generate a Deadlock situation.įirst, we will create 2 Global Temp tables CREATE TABLE #Table1 ( The best example in the SQL server is, 2 transactions are trying to update the same table at the same time. In this case, users may face application performance issues. What is Deadlock?ĭeadlock in SQL server is a scenario where two or more resources are trying to access the same resource which is mutually being locked by each other and now waiting for each other to complete. Let’s start with an introduction to Deadlock. ![]()
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