Q:  Our team has 4 people, 2 of which are web developers who use PHP to get data by using stored procedures from database. When the four of us use the system at the same time in the afternoon, SQL Server will come down. Also, at the same time, we can’t open ‘Enterprise Manager’. If we wait about 20 minutes, the system will be OK. We don’t know why this happens - why does the system lock? How can we check this out? (We are running SQL Server 2000)

Jason Hall says:  There are a couple of things that may be going on.

1) It is possible that your SQL Server or Windows OS license only allows a certain number of CALs (Client Access Licenses). If your license is capped at 4 connections, SQL Server will reject any connection made untill one of the connected users disconnects. I would check your SQL Server licensing and check your server configuraiton parameters to see if anything has been set to limit the number of concurrent connections.

2) If there is nothing in the license or server properties that would be limiting connections it is possible that the system is so overloaded that a new connection cannot be processed.
If you cannot even make a connection to the server than there is something seriously wrong with your database server. I would recommend running a diagnostic test of SQL Server to try and get a handle on what is causing these performance bottlenecks. Possibly some query is consuming so much CPU that it is causing the server to hang and reject new connections. Try running a Microsoft Profiler trace, this might help in isolating where the system hang is originating from.

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