Assume that you have a session whose deadlock priority is set to a value greater than -10 (by using the syntax of SET DEADLOCK_PRIORITY HIGH | NORMAL | LOW, or by using an integer value greater than -10). When the session executes the ALTER PARTITION FUNCTION statement, the deadlock priority of the session is temporarily set to -10 during the process, and the session is always chosen as the deadlock victim. The user-defined value isn't honored.
Because the deadlock priority mnemonics of "HIGH / NORMAL / LOW" map to their corresponding integer values of "5 / 0 / -5", setting the deadlock priority of other sessions to LOW won't help. For more information about deadlock priorities and their numeric values, see SET DEADLOCK_PRIORITY (Transact-SQL).
After you install this fix, to allow the ALTER PARTITION FUNCTION statement to honor the current user-defined session deadlock priority, use trace flag 1237.
This issue is fixed in the following cumulative update for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
Latest cumulative update for SQL Server 2016
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
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