In Oracle Workflow, Advanced Queues are used for inter-process communication, background processing, sending messages to external agents and so on. Many times the messages may not be dequeued by the consumers such as Workflow Agent Listeners or Workflow Background Engines.
Always check AQ view (AQ$<Queue_Table_Name> for message state and not the under lying table directly.
Note: In 10gR1 or later database releases, the AQ time management and many other background processes are automatically controlled by a coordinator-slave architecture called Queue Monitor Coordinator (QMNC). QMNC dynamically spawns slaves named qXXX depending on the system load.
If you want to disable the Queue Monitor Coordinator, then you must set AQ_TM_PROCESSES = 0 in your pfile or spfile. Oracle strongly recommends that you DO NOT set AQ_TM_PROCESSES = 0. If you are using Oracle Streams, setting this parameter to zero (which Oracle Database respects no matter what) can cause serious problems. So either remove AQ_TM_PROCESSES parameter or do not set its value as zero.
Note: Refer to Database Initialization Parameters for Oracle E-Business Suite Release 12 (Doc ID 396009.1) for recommendations on setting init.ora parameter JOB_QUEUE_PROCESSESPropagation takes advantage of the event based scheduling features of DBMS_SCHEDULER for better scalability. If the value of the JOB_QUEUE_PROCESSES database initialization parameter is zero, then that parameter does not influence the number of Oracle Scheduler jobs that can run concurrently. However, if the value is non-zero, it effectively becomes the maximum number of scheduler jobs and job queue jobs that can run concurrently. If a non-zero value is set, it should be large enough to accommodate a scheduler job for each Messaging Gateway agent to be started.