JOB_QUEUE_PROCESSES 參數

JOB_QUEUE_PROCESSES specifies the maximum number of job slaves per instance that can be created for the execution of DBMS_JOB jobs and Oracle Scheduler (DBMS_SCHEDULER) jobs. DBMS_JOB and Oracle Scheduler share the same job coordinator and job slaves, and they are both controlled by the JOB_QUEUE_PROCESSES parameter.

   If the value of JOB_QUEUE_PROCESSES is set to 0, then DBMS_JOB jobs and Oracle Scheduler jobs will not run on the instance.If JOB_QUEUE_PROCESSES is set to a value in the range of 1 to 1000, then DBMS_JOB jobs and Oracle Scheduler jobs will run. 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. The number of job slaves running Oracle Scheduler jobs is additionally limited to the value of the MAX_JOB_SLAVE_PROCESSES Scheduler attribute.

   Advanced replication uses Oracle Scheduler for data refreshes. 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 as well as any other features that use Oracle Scheduler or DBMS_JOB.

a、對于Oracle job進程，包含協調進程(主進程)以及奴隸進程(子進程)。
b、job_queue_processes取值范圍為0到1000，總共可創建多少個job進程由job_queue_processes參數來決定。
c、當job_queue_processes大于1時，且并行執行job時，至少一個為協調進程。其總數不會超出job_queue_processes的值。
d、job_queue_processes參數的值為且DBMS_JOB與DBMS_SCHEDULER共享。
e、job_queue_processes參數，當設定該值為0的時候則任意方式創建的job都不會運行。
f、非零值的job_queue_processes，其job子進程數依賴于可用資源，資源配置方式以及當前運行的job數來自行調整。
g、此外對于Scheduler jobs方式還受限制于scheduler屬性MAX_JOB_SLAVE_PROCESSES的設置。
h、可以通過DBMS_SCHEDULER.SET_SCHEDULER_ATTRIBUTE來設置max_job_slave_processes

此參數可以alter system立即生效