Recently, we’ve seen the ASP.Net SQL Server session state acting poorly. It seems that the clean up job was taking an abnormal amount of time. We have decided to move our session database from tempdb to its own database. Microsoft has made a KB available detailing how to persist the session database (Q311209 HOW TO: Configure ASP.NET for Persistent SQL Server Session State Management). Some more resources on ASP.Net session state are: Using SQL server for ASP.Net session state and Peter Bromberg’s Session State FAQ.