What Could Be Causing The Primary Key Exception?

My ASP pages store session variables in SQL Server with the following stored procedure: CREATE PROCEDURE [dbo].[MyProcedure] @sessionId varchar(512), @variable varc

Solution 1:

Assuming your PK is on sessionId,variable then concurrent executions of the stored procedure with the same @sessionId,@variable could do this.

Both execute the

DELETE Variables WHEREsessionId=@sessionIdANDvariable=@variable

line concurrently and then both proceed to the insert.

This could only occur if there is no pre-existing record with the sessionId,variable combination as then the DELETEs would block.