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Asked: 2026-05-10T20:21:09+00:00

When I profile my application using SQL Server Profiler, I am seeing lots of

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When I profile my application using SQL Server Profiler, I am seeing lots of Audit Login and Audit Logout messages for connections to the same database. I am wondering, does this indicate that something is wrong with my connection pooling? The reason I ask, is because I found this in the MSDN documentation in regards to connection pooling:

Login and logout events will not be raised on the server when a connection is fetched from or returned to the connection pool. This is because the connection is not actually closed when it is returned to the connection pool. For more information, see Audit Login Event Class and Audit Logout Event Class in SQL Server Books Online.

http://msdn.microsoft.com/en-us/library/8xx3tyca.aspx

Also, does anyone have any tips for determining how effective the connection pooling is for a given SQL server? I have lots of databases on a single server and I know this can have a huge impact, but I am wondering if there is an easy way to obtain metrics on the effectiveness of my connection pooling. Thanks in advance!

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  1. Remember that connections are pooled per connectionstring. If you have many databases and connect using many connectionstrings, your app will create a new connection when none exist with the correct connectionstring. Then it will pool that connection and, if the pool is full, bump an existing connection. The default Max Pool Size is 100 connections, so if you’re routinely bouncing through more than 100 databases, you’ll close and open connections all the time.

    It’s not ideal, but you can solve the problem by always connecting to a single database (one connection string) and then switch db context ‘USE [DBName]’. There are drawbacks:

    • You lose the ability to specify a user/pass per connection string (your app user needs permission to all databases).
    • Your SQL becomes more complex (especially if you’re using an out-of-the-box ORM or stored procs).

    You could experiment with increasing the Max Pool Size if your database count isn’t huge. Otherwise, if some databases are used frequently while others aren’t, you could turn pooling off on the infrequent dbs. Both items are configured via connectionstring.

    As far as metrics, monitoring the login and logout events on SQL Server is a good start. If your app is pooling nicely you shouldn’t see a lot of them.

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