Most likely you've a blocking problem. See mskb #224453 for details.

>I have one machine is accessing MS SQL Server, it submits a SQL statememnt which JOIN 3 tables which may take about 5-10 mins to return resultset.
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>When this query is running, I found that any query submitted to SQL Server after that from others machines will be blocked. The app will be like "hang", and only continue if the previous process is finished.
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