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    <p><a href="http://blog.waynesheffield.com/wayne/code-library/shred-deadlock-graph/" rel="nofollow noreferrer">Shredding your deadlock graph</a> into tabular form shows the following.</p> <pre><code>+----------+-------------------------+-----------+-----------+------------+----------+--------------------+--------------------+---------+ | LockMode | LockedObject | TranCount | LockEvent | LockedMode | WaitMode | WaitResource | IsolationLevel | LogUsed | +----------+-------------------------+-----------+-----------+------------+----------+--------------------+--------------------+---------+ | U | MYDATABASE.dbo.MyNumber | NULL | rid | X | U | RID: 5:1:127478:20 | read committed (2) | 192 | | U | MYDATABASE.dbo.MyNumber | NULL | rid | X | U | RID: 5:1:127478:16 | read committed (2) | 1848 | +----------+-------------------------+-----------+-----------+------------+----------+--------------------+--------------------+---------+ </code></pre> <p>You still haven't answered my question in the comments as to whether the sequence generation code is only called once in every transaction.</p> <p>It is easy to generate a deadlock graph similar to the one in your post if not.</p> <h2>Setup</h2> <pre><code>CREATE TABLE dbo.MyNumber ( [TYPE] CHAR(1), YRCLOSEDYN INT, NEXTNO INT ) INSERT INTO dbo.MyNumber VALUES ('X', 0, 1), ('Y', 0, 1) GO CREATE PROC MyStoredProcedure @TYPE CHAR(1), @NEXTNO INT OUTPUT AS UPDATE dbo.MyNumber SET @NEXTNO = NEXTNO = NEXTNO + 1 WHERE ( [TYPE] = @TYPE ) AND ( YRCLOSEDYN = 0 ) </code></pre> <h2>Connection 1</h2> <pre><code>BEGIN TRAN DECLARE @NEXTNO INT EXEC MyStoredProcedure 'Y', @NEXTNO OUTPUT WAITFOR DELAY '00:00:05' EXEC MyStoredProcedure 'X', @NEXTNO OUTPUT ROLLBACK </code></pre> <h2>Connection 2</h2> <p>(Run immediately after executing the code in connection 1)</p> <pre><code>BEGIN TRAN DECLARE @NEXTNO INT EXEC MyStoredProcedure 'X', @NEXTNO OUTPUT EXEC MyStoredProcedure 'Y', @NEXTNO OUTPUT ROLLBACK </code></pre> <p>The deadlock graph output from that is very similar to the one above</p> <pre><code>+----------+-------------------------+-----------+-----------+------------+----------+-----------------+--------------------+---------+ | LockMode | LockedObject | TranCount | LockEvent | LockedMode | WaitMode | WaitResource | IsolationLevel | LogUsed | +----------+-------------------------+-----------+-----------+------------+----------+-----------------+--------------------+---------+ | U | MYDATABASE.dbo.MyNumber | 2 | rid | X | U | RID: 11:1:144:1 | read committed (2) | 248 | | U | MYDATABASE.dbo.MyNumber | 2 | rid | X | U | RID: 11:1:144:0 | read committed (2) | 248 | +----------+-------------------------+-----------+-----------+------------+----------+-----------------+--------------------+---------+ </code></pre> <p>If this is the explanation for your issue you will need to ensure that you update the Sequences in the same order in all transactions (I assume there must be some good reason why you can't just use <a href="https://stackoverflow.com/a/3462957/73226">an <code>IDENTITY</code> column based solution</a>)</p>
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    1. POSQL Server 2008: U and X locks - deadlock on one table without any indexes. How?
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    1. COThank you for explanation, It is very helpful for me in the further investigation. I can't update sequences in the same order because it is done by users' actions. Also I can't use Identity due to software architecture (I definitely agree with you that IDENTITY is the best way for generating sequences). I can't do any updates to the application, I can only modify DB objects without modifying interfaces (in - out SP params etc). Thank you a lot for showing how to reproduce it.
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    2. CO@user1390785 - Well if you can't update sequences in the same order the only way of guaranteeing deadlock avoidance is to serialise access to `MyStoredProcedure` (e.g. with `sp_getapplock` but that may cause an unacceptable amount of blocking)
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    3. COIt will cause, I tried it. I now think, maybe it will be reasonable to do inserts instead of updates: insert 1 to the NEXTNO column and then take sum of this field. What do you think about it?
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