Systems Engineering and RDBMS

Do too many logins cause performance issues?

Posted by decipherinfosys on April 22, 2007

At a client site who are using SQL Server 2005, in a discussion over some other performance issues that they were having, a question was asked about the impact on performance if there are too many logins through their .Net application. In almost all the applications that we have worked on till date, unless there are connection leaks we haven’t seen this to be an issue. The default for the number of user connections allowed is very high (32767) on the server side but that was not the question – the question really was to gauge the performance impact of frequently calling Open() and Close() methods while using connection pooling (with sp_reset_connection being called to reset the state of the connection – this gets called when you have Connection Reset set to True).

We wrote a sample program and tested for up-to 5000 logins per second and that too was very un-realistic for this application. The performance impact was very low – the processor utilization remained low for the entire test. And while researching the issue, we also found an excellent blog post on the same topic by Linchi Shea who tested for a lot more number of logins per second to gauge the impact – you can read that post here.

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