SET DEADLOCK_PRIORITY (Transact-SQL)

**APPLIES TO:** ![yes](media/yes.png)SQL Server (starting with 2008) ![yes](media/yes.png)Azure SQL Database ![yes](media/yes.png)Azure SQL Data Warehouse ![yes](media/yes.png)Parallel Data Warehouse

Specifies the relative importance that the current session continue processing if it is deadlocked with another session.

Topic link icon Transact-SQL Syntax Conventions

Syntax

  
SET DEADLOCK_PRIORITY { LOW | NORMAL | HIGH | <numeric-priority> | @deadlock_var | @deadlock_intvar }  
  
<numeric-priority> ::= { -10 | -9 | -8 | … | 0 | … | 8 | 9 | 10 }  

Arguments

LOW
Specifies that the current session will be the deadlock victim if it is involved in a deadlock and other sessions involved in the deadlock chain have deadlock priority set to either NORMAL or HIGH or to an integer value greater than -5. The current session will not be the deadlock victim if the other sessions have deadlock priority set to an integer value less than -5. It also specifies that the current session is eligible to be the deadlock victim if another session has set deadlock priority set to LOW or to an integer value equal to -5.

NORMAL
Specifies that the current session will be the deadlock victim if other sessions involved in the deadlock chain have deadlock priority set to HIGH or to an integer value greater than 0, but will not be the deadlock victim if the other sessions have deadlock priority set to LOW or to an integer value less than 0. It also specifies that the current session is eligible to be the deadlock victim if another other session has set deadlock priority to NORMAL or to an integer value equal to 0. NORMAL is the default priority.

HIGH
Specifies that the current session will be the deadlock victim if other sessions involved in the deadlock chain have deadlock priority set to an integer value greater than 5, or is eligible to be the deadlock victim if another session has also set deadlock priority to HIGH or to an integer value equal to 5.

<numeric-priority>
Is an integer value range (-10 to 10) to provide 21 levels of deadlock priority. It specifies that the current session will be the deadlock victim if other sessions in the deadlock chain are running at a higher deadlock priority value, but will not be the deadlock victim if the other sessions are running at a deadlock priority value lower than the value of the current session. It also specifies that the current session is eligible to be the deadlock victim if another session is running with a deadlock priority value that is the same as the current session. LOW maps to -5, NORMAL to 0, and HIGH to 5.

**@** deadlock_var
Is a character variable specifying the deadlock priority. The variable must be set to a value of ‘LOW’, ‘NORMAL’ or ‘HIGH’. The variable must be large enough to hold the entire string.

**@** deadlock_intvar
Is an integer variable specifying the deadlock priority. The variable must be set to an integer value in the range (-10 to 10).

Remarks

Deadlocks arise when two sessions are both waiting for access to resources locked by the other. When an instance of SQL Server detects that two sessions are deadlocked, it resolves the deadlock by choosing one of the sessions as a deadlock victim. The current transaction of the victim is rolled back and deadlock error message 1205 is returned to the client. This releases all of the locks held by that session, allowing the other session to proceed.

Which session is chosen as the deadlock victim depends on each session’s deadlock priority:

SET DEADLOCK_PRIORITY is set at execute or run time and not at parse time.

Permissions

Requires membership in the public role.

Examples

The following example uses a variable to set the deadlock priority to LOW.

DECLARE @deadlock_var NCHAR(3);  
SET @deadlock_var = N'LOW';  
  
SET DEADLOCK_PRIORITY @deadlock_var;  
GO  

The following example sets the deadlock priority to NORMAL.

SET DEADLOCK_PRIORITY NORMAL;  
GO  

See Also

[@@LOCK_TIMEOUT (Transact-SQL)](../../t-sql/functions/lock-timeout-transact-sql.md)
SET Statements (Transact-SQL)
SET LOCK_TIMEOUT (Transact-SQL)