Stored procedures are timing out intermittently!

Question

I have a number of stored procedures I call from code with ExecuteNonQuery.

It was all good but 2 of my stored procedures started timing out intermittently today with:

Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. The statement has been terminated.

If I execute the sp manually from management studio it's still all good.

Nothing recently changed in my db - my command timeout is the default one.

Any clue?

EDIT

the table against the SPs are running it's huge --> 15 Gigs. Rebooted the box - same issue but this time can't get the sp to run from Management Studio either.

Thanks!

Answer 1

Is you command timeout set? Has something in your db recently changed that is causing this proc to take longer?

If you are have to diagnose locking issues, you will need to use something like sp_lock.

Can you share the source of one of your procs?

http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.commandtimeout.aspx

Answer 2

Management studio sets an infinite timeout on queries/commands it runs. Your database connection from code will have a default timeout which you can change on the command object.

Answer 3

This can often relate to:

• bad query plans due to over-eager plan-reuse (parameter sniffing)
• different SET options - in particular ANSI_NULLS and CONCAT_NULL_YIELDS_NULL
• locking (you might have a higher isolation level)
• indexing needs to be rebuilt / stats updated / etc

The SET options can lead to certain index types not being usable (indexes on persisted calculated columns, for example - including "promoted" xml/udf queries)

Answer 4

Try to recompile these procedures. I've such problems few times and didn't find the cause of problem, but recompiling always helps.

EDIT:

To recompile proc, you go to management studio, open procedure to modify and hit F5 or execute: EXEC sp_recompile 'proc_name'

Answer 5

You might need to update statistics on the database. Also has indexing on the table changed recently?

Check the execution plan of the sp to see if you can find the bottleneck. Even if it ran ok before, it can probably be tuned to run more efficiently.

Also how much data are you returning? We have had issues with poorly designed SQL in the past that didn't show up until the cumulative report starting having more data in the result set. Not knowing wht your sps do, it is hard to say if this is a possibilty, but it is worth mentioning for you to investigate.

Answer 6

SQL Server will wait indefinitely before returning to the user. More than likely there was a client side timeout property set. For example you can set a timeout property for the ADO command object.

Answer 7

Ok - this is how I fixed it in the end.

A clustered index on a table with 45 million records was killing my SQL server - every insert from code was resulting in the nasty timeouts described in the answer. Increasing the timeout tolerance wasn't gonna solve my scalability issues so I played around with indexes and making the clustered index on the primary key nonclustered unlocked the situation.

I'd appreciate comments on this to better understand how this fixed the problem.

Answer 8

Get the SQL profiler on it, compare results between running it in Management studio and via your app.