Sometimes it is useful to disable all scheduled jobs for a database (for example if you are running a performance benchmark.) You can disable each job manually and then enable them again but it is easier to set the allowed number of job processes to zero.
alter system set JOB_QUEUE_PROCESSES=0 scope=both;
Now check the setting:
show parameter JOB_QUEUE_PROCESSES
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
job_queue_processes integer 0
Now no scheduled jobs will be run.
