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we are facing application slow down and user unable to use it. for simple transaction it takes 5 to 10 minutes or not responding. but if we restart IIS & Sql Service then it work fine but only for next 4/5 hours. following is the details of application.

Application is 3 tire architecture. WCF web service project is hosted in IIS6 on server having OS Advance Server 2003 and SQL Server 2005 is on the same server and client application is separately install on every client machine (approx. 50 users) by click once deployment. For data access we have used Microsoft Enterprise Library. application developed on framework 3.0.

any help will be really appreciated. Thanks in advance.

Sunil
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    Impossible to help without some code and more detail. – Daniel Kelley Jul 02 '14 at 07:49
  • Sounds like you got some sort of retry for the SQL commands that fail. Each command gets pushed into a queue and then executed. Commands that fail pile up and causes your server to slow down. But this is just a guess...Try to use some logging for each query and mabye use a profiler. – dburner Jul 02 '14 at 07:56
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    Could be server memory running out? SQL Server will continue to use more and more RAM until a given threshold, initially you could be fine when there's plenty available, after some usage it will be at the max level and starting to spill onto disk. – Chris L Jul 02 '14 at 08:11
  • What's your throughput? If it's too high, you can implement throttling in IIS: http://stackoverflow.com/questions/33969/best-way-to-implement-request-throttling-in-asp-net-mvc – tom redfern Jul 02 '14 at 08:23

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Well there are so many possible reasons of this starting from poor written queries, lacking of useful indexes etc. It's hard to tell anything really useful without any details. However I recommend getting familiar with sys.dm_os_wait_stats dynamic view in SQL Server. It is a very good starting point. Check out this great article: http://www.mssqltips.com/sqlservertip/1949/sql-server-sysdmoswaitstats-dmv-queries/

And be aware that all the information stored in DMVs is lost whenever you restart SQL Server. It's complicates the troubleshooting and considered as a bad practice, try to avoid it.

Andrei Shakh
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