Thursday, April 1, 2010

Concurrent connections to SQL server or SQL express

SQL server or SQL express supports unlimited (maxint) number of concurrent connections. SQL server installation wizard asks for number of connections to limit to. If the value given is 0 then it means unlimited number of connections. User can specify any number of connections that he wants.

It is a myth that SQL server or SQL express supports only 5 concurrent connections. There is some history behind it. Microsoft came up with MSDE engine to overcome limitations of popular Jet database engine. The initial version of MSDE engine could allow maximum 5 concurrent connections as the performance detoriorates if more than 5 concurrent connections are made to the MSDE database engine. Governor component in MSDE engine used to control the maximum connections.

The latest versions of SQL server (I guess SQL 2000 onwards) and SQL express does not have governor component. So now what limits the concurrent connections is now how the connection is made, for how much time and how it is used.

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