This message has come across my desk a couple of times in the last week and when that happens I like to produce blog content.
The error is when you are trying to use a pooled connection and the reset of the connection state encounters an error. Additional details are often logged in the SQL Server error log but the 'failure ID' is the key to understanding where to go next.
Event ID: 18056
Description: The client was unable to reuse a session with SPID 157, 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.
Read more: CSS SQL Server Engineers Part 1, Part 2
The error is when you are trying to use a pooled connection and the reset of the connection state encounters an error. Additional details are often logged in the SQL Server error log but the 'failure ID' is the key to understanding where to go next.
Event ID: 18056
Description: The client was unable to reuse a session with SPID 157, 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.
Read more: CSS SQL Server Engineers Part 1, Part 2