What will happen to the Oracle Queue if the database crashes and restarts? Do we have to manually restart the queue again? Will there be inconsistent transactions or is oracle database server intelligent enough to handle that?
If manual restart of the queue is needed after a database restart is it ideal to create a job to start the queue automatically?
You do not need to manually start the queues. But depending on the criticality of the database, you may want to create a job that, upon startup, will ensure that everything is properly set up (http://www.dba-oracle.com/t_database_startup_trigger.htm).
There will be no inconsistent data. Oracle ensures that no data is lost except for ongoing transactions. Those will be rollbacked.