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Questions tagged [deadlock]

A situation caused by two or more processes being unable to proceed (and thus release their locks) because they are blocked by locks on resources held by the other process.

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55
votes
6answers
66k views

What are the main causes of deadlocks and can they be prevented?

Recently one of our ASP.NET applications displayed a database deadlock error and I was requested to check and fix the error. I managed to find the cause of the deadlock was a stored procedure that was ...
32
votes
5answers
28k views

Handling concurrent access to a key table without deadlocks in SQL Server

I have a table that is used by a legacy application as a substitute for IDENTITY fields in various other tables. Each row in the table stores the last used ID LastID for the field named in IDName. ...
30
votes
1answer
42k views

SQL Server: deadlocked on lock communication buffer resources

What could be possible reason for this deadlock type? (not deadlock in general) Lock communication buffer resources Is this indicated system is low in memory and buffers count ran out of limit? ...
29
votes
5answers
3k views

SQL Deadlock on the same exclusively locked clustered Key (with NHibernate) on delete / insert

I have been working on this deadlock issue for quite a few days now and no matter what I do, it persists in one way or another. First, the general premise: We have Visits with VisitItems in a one to ...
26
votes
3answers
30k views

Code to simulate deadlock

I am testing my application I need some code that stable simulates the deadlock on database site (sql script if possible). Thank you. ADDED: Reproducing deadlocks involving only one table
22
votes
4answers
19k views

Merge statement deadlocking itself

I have the following procedure (SQL Server 2008 R2): create procedure usp_SaveCompanyUserData @companyId bigint, @userId bigint, @dataTable tt_CoUserdata readonly as begin set ...
18
votes
2answers
3k views

Can foreign keys cause deadlocks and hinder READ COMMITTED SNAPSHOT?

This is a followup question from: https://stackoverflow.com/questions/7684477/is-it-possible-to-set-transaction-isolation-level-snapshot-automatically I'm still having deadlock/timeout situations in ...
17
votes
2answers
9k views

Deadlocks From Locks on Same Temporary Tables In Different Processes

I have found a deadlock that appears to show something I thought was impossible. There are two processes involved in the deadlock: 1. process8cf948 SPID 63 Performing an ALTER TABLE on temporary ...
16
votes
2answers
6k views

Trouble deciphering a deadlock in an innodb status log

We are accessing MySQL from the Microsoft ADO.NET connector. Occasionally we are seeing the following deadlock in our innodb status and haven't been able to identify the cause of the problem. It ...
16
votes
1answer
3k views

Resolving deadlock from 2 tables only related through indexed view

I have a situation where I'm getting deadlocks, and I think I've narrowed down the culprits, but I'm not quite sure what I can do to fix it. This is on a production environment running SQL Server ...
15
votes
4answers
9k views

How can I convert a key in a SQL Server deadlock report to the value?

I have a deadlock report that tells me that there was a conflict involving waitresource="KEY: 9:72057632651542528 (543066506c7c)" and I can see this: <keylock hobtid="72057632651542528" dbid="9" ...
15
votes
3answers
22k views

Notification on long-running query or deadlock in SQL Server 2008 R2?

I'd like to know if there is a way to send a notification on deadlock? If so what queries would be required. I understand that SQL Server takes care of deadlocks, I simply would like information on ...
15
votes
2answers
2k views

Simultaneous calls to the same function: how are deadlocks occurring?

My function new_customer is called several times per second (but only once per session) by a web application. The very first thing it does is lock the customer table (to do an 'insert if not exists'&...
13
votes
2answers
8k views

Deadlock error isn't returning the deadlock SQL

Transaction (Process ID) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction. I am getting this error randomly when one of my ...
13
votes
3answers
12k views

Can I create a user defined table type and use it in the same transaction?

When I execute the following (in management studio, GO will separate the commands into batches) use tempdb begin tran go CREATE TYPE dbo.IntIntSet AS TABLE( Value0 Int NOT NULL, Value1 Int ...
13
votes
2answers
8k views

SQL Server Index Update Deadlock

I have 2 queries which when run at the same time are causing a deadlock. Query 1 - update a column which is included in an index (index1): update table1 set column1 = value1 where id = @Id Takes X-...
12
votes
2answers
6k views

Will these two queries result in a deadlock if executed in sequence?

This is almost certainly the cause of my other question, but I thought it was worth separating the two as I have a hypothesis based on the following log that I would love to have falsified or verified....
12
votes
1answer
197 views

SQL Extended Events Session for deadlock detection

Is there a way to increase the size of the <inputbuf> element in the deadlock XML captured by the deadlock extended events session? We want to see the complete query to help pinpoint the issue ...
11
votes
6answers
4k views

Best situation to use READ UNCOMMITTED isolation level

As we all know, READ UNCOMMITTED is the lowest isolation level in which things like dirty reads and phantom reads may accrue. When is the best time to use this isolation level and for what reasons ...
11
votes
2answers
8k views

Why does this query cause a deadlock?

Why does this query cause a deadlock? UPDATE TOP(1) system_Queue SET [StatusID] = 2, @ID = InternalID WHERE InternalID IN ( SELECT TOP 1 InternalID FROM system_Queue WHERE ...
11
votes
2answers
9k views

Good reasons to use SELECT… WITH XLOCK?

I am facing some re-occurring deadlocks, one of which is a Keylock and contains a SELECT query with XLOCK hint that becomes the deadlock victim. The other statement is an INSERT into one of the tables ...
11
votes
5answers
12k views

How to monitor deadlocks

When do you start troubleshooting a SQL Server 2005/2008 deadlocks and how? The alert is turned on SSMS via SQL Server performance condition alert, objects->SQLServer:Locks, Counter->Lock Waits/Sec, ...
11
votes
1answer
14k views

Deadlock on Delete Statement

I get a deadlock when a SQL Server Job runs. The deadlock occurs on a simple DELETE statement. I would have thought there would have to be a SELECT/UPDATE query running to cause the deadlock? But ...
11
votes
1answer
10k views

SQL Server Deadlock on two updates due to index lock order

I have two UPDATEs - one locks the CI first and then the NCI (on status) because the status column is also being updated. The other already owns a U lock on the NCI because it knows it is changing ...
11
votes
1answer
3k views

Why are there Victimless Entries on the Deadlock Graph?

I am trying to learn how to analyze SQL Server 2008's deadlock graph, and I'm finding alot of entries with an empty <victim-list> node. I don't understand what these entries represent: if there ...
10
votes
2answers
23k views

How can I configure MySQL Innodb to handle 1000s of inserts per hour?

I have a very high traffic website where it is possible that 1000s of new records are inserted every hour. This one error is crippling the site: PDOException: SQLSTATE[40001]: Serialization failure: ...
10
votes
1answer
12k views

Meaning of 'locks rec but not gap waiting' in deadlock report

About the meaning of locks rec but not gap waitingin TRANSACTION(1), which one is correct? Already granted gap lock, waiting for clustered index X lock? Already granted clustered index X lock, ...
10
votes
1answer
13k views

View last several innodb deadlocks

I see that I can view the latest deadlock in mysql/innodb, but is there a way to view past deadlocks? We have two deadlock issues, one being important and the other not. The less important deadlock ...
10
votes
2answers
2k views

Tablock hint triggers deadlocks

I was inserting two data sets, using minimal logging, into an empty heap table using via two Execute SQL Tasks running in parallel and with SQL of the following form. INSERT INTO Table (TABLOCK) ...
10
votes
2answers
2k views

If a Parallelism Exchange Event deadlock is victim-less, is it a problem?

We're seeing a lot of these Intra-Query Parallel Thread Deadlocks in our Production environment (SQL Server 2012 SP2 - yes...I know...), however when looking at the Deadlock XML that has been captured ...
10
votes
1answer
806 views

When does SQL Server acquire locks?

The list of isolation levels in SQL Server found here states that write locks acquired within a transaction are retained until the end of the transaction. However it doesn't mention anything about ...
10
votes
2answers
1k views

How does SQL Server determine the order it takes locks in while selecting a table?

I have two stored procedures that are deadlocking when the system is under load. Proc A is selecting from a table while the Proc B is inserting into the same table. The Lock Graph is showing that Proc ...
9
votes
2answers
8k views

SELECT/INSERT Deadlock

This instance hosts the SharePoint 2007 databases (SP). We have been experiencing numerous SELECT/INSERT deadlocks against one heavily utilized table within SP content database. I have narrowed down ...
9
votes
1answer
8k views

Optimizing concurrent updates in Postgres

I'm running concurrent Postgres queries like this: UPDATE foo SET bar = bar + 1 WHERE baz = 1234 Each query affects the fixed K number of rows, and I can't find a way to enforce the order in which ...
9
votes
3answers
719 views

Need Help Troubleshooting Sql Server 2005 Deadlock Scenario

I am running into a deadlock scenario where the only participants in the deadlock appear to be a single table and a single stored procedure that deletes from that table. I drew that conclusion based ...
9
votes
1answer
9k views

MySQL InnoDB Deadlock For 2 simple insert queries

I have a deadlock for this two insert queries: insert into PlayerClub (modifiedBy, timeCreated, currentClubId, endingLevelPosition, nextClubId, account_id) values (0, '2014-12-23 15:47:11.596', 180, ...
9
votes
1answer
501 views

What does “*password------------” mean in a profile deadlock report?

In SQL Server 2008 R2, I got several deadlock reports that have "*password------------" in the input buffer. It looks like an attack but in that case I don't know the reason or the kind of attack. (...
9
votes
1answer
5k views

SQL Server Deadlock Graph - Table, Page or Row Lock?

Is there any way to decipher if a lock in a deadlock graph is Table, Page or Row level? I have all the information I need from the graph, including the Isolation Level, (2) but I really want to know ...
9
votes
2answers
240 views

How to Prevent Partitioned Columnstore Deadlocks on SELECT

I have three Clustered Columnstore Index (CCI) tables in SQL Server 2016. All of these CCIs are in the same partitioning scheme, based on Tenant ID. Lately, and inconsistently, I am getting deadlocks ...
9
votes
1answer
426 views

Overcome MERGE JOIN(INDEX SCAN) with explicit single KEY value on a FOREIGN KEY

Added 7/11 The issue is deadlocks occur because of index scan during MERGE JOIN. In this case a transaction trying to get S lock on the whole index at the FK parent table, but previously another ...
9
votes
1answer
249 views

Apparently, my CLR assembly function is causing deadlocks?

Our application needs to work equally well with an Oracle database or a Microsoft SQL Server database. To facilitate this, we created a handful of UDFs to homogenize our query syntax. For example, SQL ...
8
votes
1answer
730 views

UPDATE heap table -> Deadlocks on RID

I'm setting up a test case to prove a certain deadlock scenario and require some insight on what is going on. I have a heap table, conventiently called HeapTable. This table is updated by 2 ...
8
votes
1answer
1k views

How are deadlocks detected and reported in an RDBMS?

I was given this essay type question during an interview but did not get the job. The full question was as follows: How are deadlocks detected and reported in an RDBMS? What are the transaction ...
8
votes
3answers
5k views

Why does this query result in deadlock?

I provide below the raw MySQL query and also the code in which I do that programatically. If two requests are being done at the same time results in the following error pattern: SQLSTATE[40001]: ...
8
votes
1answer
2k views

MERGE deadlocking prevention

In one of our databases we have a table that is intensively concurrently accessed by multiple threads. Threads do update or insert rows via MERGE. There are also threads that delete rows on occasion, ...
8
votes
2answers
5k views

MySql Gap Lock Deadlock on Inserts

I'm getting Deadlocks from gap locks on a table when inserting into it frequently from multiple sources. Here is an overview of my processes. START TRANSACTION UPDATE vehicle_image SET active = 0 ...
8
votes
1answer
7k views

Are InnoDB Deadlocks exclusive to INSERT/UPDATE/DELETE?

I am Working around MySQL error "Deadlock found when trying to get lock; try restarting transaction". I am going to have to update a program to allow deadlocks. Is it possible that SELECT statement ...
8
votes
2answers
723 views

SQL Server Select Count READ_COMMITTED_SNAPSHOT QUESTION

I seem to be getting a lot of deadlocks when doing select count(*) on a particular table. I have already changed all the required parameters and made them into row only locking. I've also changed the ...
8
votes
1answer
1k views

Trace Flag 1222 Not Working?

I have a customer site with two similarly configured 2008r2 SQL Servers "A" and "C". On both servers the trace flags 1204 and 1222 are enabled and DBCC tracestatus shows the following on both servers:...
7
votes
4answers
5k views

Are deadlocks a serious problem? [closed]

I have a few production SQL Server instances and I get around 100 deadlock alert emails a day (up to 100 for one server, 150 in total). Is this a problem I should investigate? How many deadlocks are ...