PDB does not log exception thrown by connection.close()

[rfer]

Transcript from the original issue reported in the internal issue tracker.

PDB does not log exception thrown by connection.close(), merely reporting that an error has occurred.
JDBC API states the following on close()
It is strongly recommended that an application explicitly commits or rolls back an active transaction prior to calling the close method. If the close method is called and there is an active transaction, the results are implementation-defined.
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The DB2 JDBC implementation throws an exception if a transaction is still active on close(). It does not close the transaction, so if the transaction is still active and holding on to locks, they will be "alive" for a long time (whatever the timeout is) causing deadlocks. While not closing the transaction is a a project issue (which we fixed), not reporting the exception makes troubleshooting much harder.