DBMS_JOB and Oracle Scheduler share the same job coordinator and job slaves, and they are both controlled by the JOB_QUEUE_PROCESSES parameter. The actual number of job slaves created for Oracle Scheduler jobs is auto-tuned by the Scheduler depending on several factors, including available resources, Resource Manager settings, and currently running jobs. However, the combined total number of job slaves running DBMS_JOB jobs and Oracle Scheduler jobs on an instance can never exceed the value of JOB_QUEUE_PROCESSES for that instance.

• In a non-CDB:

  Set JOB_QUEUE_PROCESSES to the maximum number of job slaves that can be used simultaneously in the entire database instance. If JOB_QUEUE_PROCESSES is 0, then DBMS_JOB jobs and Oracle Scheduler jobs will not run in the database instance.

• In a CDB root:

  Set JOB_QUEUE_PROCESSES to the maximum number of job slaves that can be used simultaneously in the entire CDB. If JOB_QUEUE_PROCESSES is 0 in a CDB root, then DBMS_JOB and Oracle Scheduler jobs cannot run in the CDB root or in any PDB, regardless of the JOB_QUEUE_PROCESSES setting at the PDB level.

• In a PDB:

  Set JOB_QUEUE_PROCESSES to the maximum number of job slaves that can be used simultaneously in the PDB. The actual number depends on the resources assigned by Resource Manager and the demand in other containers. When multiple PDBs request jobs, Oracle Scheduler attempts to give all PDBs a fair share of the processes. If JOB_QUEUE_PROCESSES is 0 in a PDB, then DBMS_JOB and Oracle Scheduler jobs cannot run in the PDB, regardless of the JOB_QUEUE_PROCESSES setting in the CDB root.

Oracle Streams Advanced Queuing uses Oracle Scheduler for message propagation. Materialized views use Oracle Scheduler for automatic refreshes. Setting JOB_QUEUE_PROCESS to 0 will disable these features and any other features that use Oracle Scheduler or DBMS_JOB.