One of the most frequent error messages I come across when dealing with SQL Server, particularly SQL Server 2008 R2, is Error 18056, Severity: 20, State: 29. Not only do I constantly see this error message in the SQL logs, but also in the Microsoft community forums. I often see inquiries likes, “I have SQL Server 2008 R2 SP2 installed and I see the error below. I have the most recent Service Pack installed, but the problem remains.”
Error: 18056, Severity: 20, State: 29.
The client was unable to reuse a session with SPID XXXX, which had been reset for connection pooling. The failure ID is 29. This error may have been caused by an earlier operation failing. Check the error logs for failed operations immediately before this error message.
Now, this error message can be triggered by many things. For instance, lack of user permissions in any database, or in the worst case, lack of resources in the server that made it stop accepting new connection requests. However, in any of those cases you would probably have a lot of angry users calling you and complaining that they can’t do their work. If that’s not the case, you are probably just seeing a generic and internal error message that shouldn’t be in the SQL error log in the first place.
The first step to addressing this issue, or simply investigating if it’s something more serious, is to update to the latest Cumulative Update.
Microsoft released a fix that makes SQL Server stop logging this generic error message in some cases, when it’s not important for you to investigate the issue.
I hope this help you to get rid of this error message.