We have an web application that uses a Sybase/JDBC Datasource. We are utilziing the standard connection pooling provided by WebSphere 5 and the jConnect JDBC provider. We are experiencing intermittent SqlExceptions "JZ0C0: Connection is already closed." when attempting to use connections returned from the Datasource. We're fairly confident we are dutifully closing all of our statements, result sets and connections when we are done using them. It is our understanding that when we close a connection, it is returned to the connection pool and is available for further use.
This appears to work properly most of the time. We have not been able to reproduce it reliably.