Never use DDL or DML against tables created by
dbms_aqadm.create_queue_table. Only use dbms_aqadm and dbms_aq to work with these tables. Oracle may make several supporting tables, indexes, etc that you will not be aware of. Manually running DDL or DML against the table may lead you to a scenario where Oracle Support will need you to drop and recreate the table and queues to resolve the situation.
It's strongly recommended you do not use
dbms_aq.forever for a wait option. This has caused issues in the past as Oracle may start scheduling an excessive number of worker jobs to work the queues that are unnecessary (see Oracle Doc ID 2001165.1).
It's recommended you do not set the AQ_TM_PROCESSES parameter in version 10.1 and later. Especially avoid setting this to zero since this will disable the QMON background job that is necessary to maintain the queues. You can reset this value to the Oracle default using the following command and restarting the database.
alter system reset aq_tm_processes scope=spfile sid='*';