>>>>Hi,
>>>>
>>>>My application creates one SQL Server connection at the top of the application and then relies on it for all calls to SQL Server. But I understand that the connection can time out. Therefore, do you recommend that the program checks if the connection is still valid (by e.g. by SELECT CAST(1 as BIT) or some other way) every time the program needs to connect (to SQL Select or Update)? TIA.
>>>
>>>See: http://msdn.microsoft.com/en-us/library/8xx3tyca.aspx
>>>
>>>When you close a connection in code you will just be returning it to the pool. Likewise, when you open, you will usually be getting an existing connection from the pool.
>>>Given the above it is usually best practice to keep a connection open in code for the minimum possible time - ideally wrap it in a using....
>>
>>Does every SQL Server maintains this "connection pool"? Also, what about the fact that the application will slow down if it has to make connection frequently. I notice that when my application makes the first connection it takes a couple of few seconds. If this will be occurring repeatedly I don't think my customers will be happy.
>>Thank you for your input.
>
>It''s not a SQL Server thing - it's ADO.NET functionality. The link I provided explains in detail how this works.
>
>The *very first time* you open the connection you will incur the overhead of 'physically' connecting to the server. But closing the connection does not physically close it - it is just returned to the pool. Next time you ask for the same connection you will probably get the already opened connection from the pool - therefore no noticeable overhead.....

Thank you for the explanation. I didn't look in the link but will do that.