Oracle Message ORA-24018 - STOP_QUEUE on string failed, outstanding transactions found

ERRORSTOP_QUEUE on string failed, outstanding transactions found
CAUSEThere were outstanding transactions on the queue, and WAIT was set to false, so STOP_QUEUE was unsucessful in stopping the queue.
ACTIONSet WAIT to TRUE and try STOP_QUEUE again. It will hang till all outstanding transactions are completed.