ah, thanks you pointed me in the right direction after some investigations I found out, that the READ_COMMITED transaction isolation level behaves differently between oracle and MS Sql server. SQL Server uses shared locks by default. Thus the select statement is blocked while the update is not commited yet. If you set READ_COMMITTED_SNAPSHOT to ON for your database, then it uses row-versioning (like Oracle's default mode): and the select will not be blocked until the update is commited. I think this behaviour can improve performance on my webapplication. more information on this: http://msdn2.microsoft.com/en-us/library/ms173763.aspx http://msdn2.microsoft.com/en-us/library/tcbchxcb(VS.80).aspx View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4138009#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...