This appears to be a known issue that is fixed in SEP12.1RU3:
Database connection log contains database connection warnings
Fix ID: 3075314
Symptom: The db-connection.log contains the warning:
<computercode style="font-family: 'Courier New'; font-size: 12pt; color: rgb(34, 34, 34); line-height: 20px;"></computercode><computercode style="font-family: 'Courier New'; font-size: 12pt; color: rgb(34, 34, 34); line-height: 20px;">WARNING: ClientTransportInfoTask: (db conn) Return Connection Error-> can't find connection (hashcode=X) in the map, total count=0</computercode>
Solution: Fixed an issue in the database connection logic to resolve this warning.
http://www.symantec.com/docs/TECH206828