job interval vs job_queue_interval

Could anyone give me some explaination how it works?
job_queue_interval in init.ora and interval in a job

I am setting up a snapshot refresh group with interval 10 second and set job_queue_interval=20 in init.ora. It seems refresh time about 10 seconds. if job queue wake up every 20 seconds how it possible do refresh less than 20 seconds?
when I reverse it, job_queue_interval=10 and job interval=20,
it seems still refresh in 10 seconds.

currecntly I manually check the result to get timing, does any view can help me to figure out the "true" refresh time?

thanks in advance

In either case the lowest value takes the prceedence. When you get to set the job_queue_interval it would apply to all the jobs and it would awake the jobs in the order, after the specified period of time. When you say interval in the jobs, it would be applicable to the job but if the value of job_queue_interval was set low, then that would take preceedence over the interval value. B'cos both of them would go and awake the SNPn process to get their activity going on.

Hope this would help you,
Sam