Hi,

I'm using SQL Server 2008 on Windows Server 2008 R2, all sp'd up.

I'm getting occasional issues with SQL Server hanging with the CPU usage on 100% on our live server. It seems all the wait time on SQL Sever when this happens is given to SOS_SCHEDULER_YIELD.

Here is the Stored Proc that causes the hang. I've added the "WITH (NOLOCK)" in an attempt to fix what seems to be a locking issue.

ALTER PROCEDURE [dbo].[MostPopularRead]
AS
BEGIN
SET NOCOUNT ON;

SELECT 
    c.ForeignId , ct.ContentSource as ContentSource
    , sum(ch.HitCount * hw.Weight) as Popularity
    , (sum(ch.HitCount * hw.Weight) * 100) / @Total as Percent
    , @Total as TotalHits
from 
    ContentHit ch WITH (NOLOCK)
    join [Content] c WITH (NOLOCK) on ch.ContentId = c.ContentId
    join HitWeight hw WITH (NOLOCK) on ch.HitWeightId = hw.HitWeightId
    join ContentType ct WITH (NOLOCK) on c.ContentTypeId = ct.ContentTypeId
where 
    ch.CreatedDate between @Then and @Now
group by
    c.ForeignId , ct.ContentSource
order by
    sum(ch.HitCount * hw.HitWeightMultiplier) desc
END

The stored proc reads from the table "ContentHit", which is a table that tracks when content on the site is clicked (it gets hit quite frequently - anything from 4 to 20 hits a minute). So its pretty clear that this table is the source of the problem. There is a stored proc that is called to add hit tracks to the ContentHit table, its pretty trivial, it just builds up a string from the params passed in, which involves a few selects from some lookup tables, followed by the main insert:

BEGIN TRAN
insert into [ContentHit] 
    (ContentId, HitCount, HitWeightId, ContentHitComment)
values
    (@ContentId, isnull(@HitCount,1), isnull(@HitWeightId,1), @ContentHitComment)
COMMIT TRAN

The ContentHit table has a clustered index on its ID column, and I've added another index on CreatedDate since that is used in the select.

When I profile the issue, I see the Stored proc executes for exactly 30 seconds, then the SQL timeout exception occurs. If it makes a difference the web application using it is ASP.NET, and I'm using Subsonic (3) to execute these stored procs.

Can someone please advise how best I can solve this problem? I don't care about reading dirty data...

Thanks