Query times out when executed from web, but super-fast when executed from SSMS

Question

I\'m trying to debug the source of a SQL timeout in a web application that I maintain. I have the source code of the C# code behind, so I know exactly what code is running.

Answer 1

If you can change your code to fix parameter sniffing optimize for unknown hint is your best option. If you cannot change your code the best option is exec sp_recompile 'name of proc' which will force only that one stored proc to get a new execution plan. Dropping and recreating a proc would have a similar effect but could cause errors if someone tries to execute the proc while you have it dropped. DBCC FREEPROCCACHE drops all your cached plans which can wreck havoc ok your system up to and including causing lots of timeouts in a heavy transactions production environment. Setting arithabort is not a solution to the problem but is a useful tool for discovering if parameter sniffing is the issue.