Hello Tapomay (and list), I have a theory to your issue: MonetDB (and the MonetDB JDBC driver for that matter) requires you to rollback a failed transaction before you can work with that connection again. This is consistent with the JDBC documentation [1]. The reason why you get the error in the connection check query is that C3P0 transparently executes this query in the background, which results in the error "!25005!current transaction is aborted (please ROLLBACK)". In your sample code, I could find a rollback() method but no evidence it is actually used, so please check this again in you application. That all being said, looking at the stack trace you have provided (process hanging on socket IO), tells me that there is a possibility for a protocol misunderstanding between MonetDB and JDBC. However, without further information from you (and preferably a failing-yet-semantically-correct test case) it is very difficult to investigate this further. Best, Hannes [1] http://docs.oracle.com/javase/tutorial/jdbc/basics/transactions.html#call_ro... _______________________________________________ users-list mailing list users-list@monetdb.org http://mail.monetdb.org/mailman/listinfo/users-list