SQL Server taking a long time to return data to ColdFusion when using Flex

Question

I am working on a Flex application that is connecting via Flash Remoting to ColdFusion 8 with a SQL Server 2005 database. Most of the time, everything runs fine. However, from time to time, it will take an exceptionally long time for SQL Server to return data from a stored procedure call to ColdFusion; returning data from CF to Flex is very fast. When this happens, I can run the exact same call from Management Studio on the SQL Server or a ColdFusion page on the CF server and get results immediately. The most recent occurrence of the issue took about 90 seconds to return data to CF. During the 90 second window, I was able to run the stored procedure in Management Studio several times.

I have tried using different drivers and this doesn't seem to matter. I have also kept an eye on server performance and haven't noticed anything unusual while this is happening. Has anyone seen this behavior before? Any ideas as to what I should be looking for.

Answer 1

While it's working slowly, can you run "sp_who2" against your SQL Server? If it's a blocking issue, you'll see rows that have a value in the "BlkBy" column, meaning that they'r waiting for another process to complete before they can continue.

If that's the case, then there's other troubleshooting to do so you can figure out what's causing the blocks. This article provides an overview of locking and troubleshooting blocks. If that's your issue, please update your question and add more details, and we can help you go from there!

Answer 2

Are you absolutely sure that the query being run in the sp is the same every time? For example, is it possible that when it slows down, the query has a different sort order? Possibly 9 times out of 10, the query returns quickly, and that 10th time is slow b/c the data you're getting is being sorted by some column that isn't indexed?

In these situations, I'd try to have a SQL Trace set up (using sql profiler) and let it run for a while. Once the situation happens, let it run through, and then analyze the trace. Confirm beyond doubt that the query being run is the same as other executions of the same sp